Anyone who paid close attention to papal liturgies during the previous and current pontificates has noticed a distinct change in style. The liturgies of John Paul II were massive, almost Hollywoodesque affairs, often utilizing styles from the regions of the world in which the Roman Church is expanding. These were liturgies of cultural scope and (at times) content, attempts to apply the principle of inculturation on the grand liturgical stage. They were, for twenty five years, representative of the typical model of liturgical theory (or interpretation of Sacrosanctum Concilium) that came to dominate many Western (certainly American) theological centers. When Benedict XVI assumed the papacy, a shift in liturgical style was detectable - or, to be blunt, it was clearly manifest. Benedict quickly appealed to the historical mode of liturgical celebration in the Latin Church. Latin itself became more common (as has been use of Missale Romanum of Paul VI as opposed to the Italian Messale Romano) and sacred polyphony has returned to the Roman choirs. These are all part of a larger liturgical shift that has occurred during Benedict's papacy and which have had, to varying degrees, influence beyond the Sistine Chapel.
During his time as head of the CDF, at least since the Lefevbre affair in 1988. Joseph Ratzinger represented a model for interpreting Sacrosanctum Concilium that ran contrary to the school of thought that became dominant in the years after the Council's conclusion. Upon his election to the papal throne, the underground current of liturgical theory finally came to force. The past eight years have seen a gradual attempt to put much of this school's theory into liturgical praxis.
Benedict accelerated his return to a typical "Latin" celebration of the liturgy when he appointed a new papal master of ceremonies. The pontifical masses increased in solemnity and many liturgical items that had seemingly been discarded after the Council were appropriated for use. These visuals were combined with the increasing use of Latin and chant with the intention of rediscovering an aura of the sacred in the Roman liturgy. How effective has this been? There have been some notable attempts to duplicate Benedict's liturgical style at the parish level. It must be noted that these are, by and large, typically done by priests or parishes with an active online presence, however, they also represent a minority. The average American parish, for instance, has not seen many notable changes in the celebration of the ordinary form of the Roman rite.
For years, Joseph Ratzinger was also the most prominent proponent in the Vatican for liberalizing the celebration of the pre-Conciliar Missale Romanum. Not only for reconciling certain break away groups, but also under the conviction that the old Missale Romanum has much to offer the Roman Church. Shortly after his election to the papacy, rumors began circulating that Benedict intended to grant a universal indult for the Missale Romanum of 1962. In July of 2007, Benedict released the motu proprio Summorum Pontificum and its accompanying explanatory letter. Therein, Benedict adjudicated that the "Tridentine" Missal had not been abbrogated by Paul VI propagation of the Missale Romanum of 1970. Additionally, priests were within their rights to celebrate it and the laity were within their rights to be provided with a celebration of the old liturgy. Since then, there has been a steady stream of successes and failures to establish regular "Tridentine" liturgies in parishes that previously lacked a priest with an Ecclesia Dei indult.
Of course, for English speaking Catholics, the most notable liturgical item of Benedict's papacy is the Third Edition of the Roman Missal and its significantly revised translation. The project was at least a decade in the making and the results, thus far, seem mixed. There was much drama from certain quarters, although the predictions of rebellion and incomprehension have proven baseless. Much that was left untranslated in the previous English edition has finally found expression. It remains unclear if the new translation has succeeded in revealing the supernatural realm to the religious body, although I suspect those persons who would normally have an interest in liturgy have more to chew on, as it were.
These are the three things that immediately come to mind when reflecting upon the liturgy in Benedict's pontificate. Others may likely have additional entries, although these seem to me to be the most notable. With every milestone in one pontificate, there are corresponding questions in another. Precisely what will remain going forward is any one's guess. While Benedict may have appointed a significant portion of the cardinal electors (presumably they share some affinity with his thought) it must be recalled that the remainder are appointees from John Paul II's pontificate. John Paul, as mentioned, had and cultivated a different approach to liturgy compared to his successor. We may or may not see some of evidence of this distinction in the future pontiff.
It seems the new English translation safe. Simply, too many bishops from Africa favored a new translation of the English text (including Cardinal Arinze). There will be no return to the previous English text. This edition is here to stay, at least until the liturgical calendars have been fulfilled (around the year 2039). Most publishers designed their books for long term use. Additionally, the expenses invested in producing the translation, creating educational materials and, finally, purchasing the new books will likely slow down any motions to revise the new translation for the foreseeable future.
Whether or not Benedict's celebration of the liturgy, the example he provided from St. Peter's, will survive into the next pontificate is more complicated. There have been attempts (by web savy priests or parishes) to incorporate Benedict's style at the parish level to varying degrees. How much Benedict's liturgical theory represents the direction in which things will go largely depends upon how well his thought represents the thought of the cardinal electors and the episcopate as a whole. If this is not simply Benedict's pet theory, then it is likely his successor will continue with this manner of celebration to one degree or another. Ultimately, whether or not Benedict's liturgical praxis reorients liturgy in the Latin Church is contingent upon how well his liturgical theology is diffused in the Roman Church. Benedict's liturgical praxis is a result of his liturgical theology, a liturgical theology that often runs contrary to the minimalist theology of the post-Vatican II liturgical establishment. It will not be popularly understood or accepted, although its success will be measured by whether or not the "right people" in the right ecclesiastical places utilize it to any appreciable degree. If Benedict's liturgical theology succeeds in becoming the new reference point for future Roman Catholic liturgical theology, then it is likely his liturgical praxis will influence even the most common parish liturgies over time. For what it's worth, it seems to me that in a world of minimalist liturgical theology, Benedict stands a good chance of being remembered for his liturgical work.
Benedict's decisions regarding the old liturgy are perhaps the liturgical item that whose fate in the immediate future is most uncertain. Summorum Pontificum was greeted with division among Benedict's cardinals, to the degree that he had to both summon a group of representative cardinals to the Vatican and address the matter in the explanatory letter that accompanied the motu proprio. Among the most notable cardinals who expressed disagreement with Benedict's measure was Cardinal Arinze, who reportedly felt the motu proprio undermined the bishop's authority over the liturgy in his own diocese. Other cardinals were simply indisposed towards any sort of revival of the "Tridentine" liturgy. Even among the cardinals and bishops appointed during Benedict's pontificate, one is hard pressed to find a consistent approach and appreciation of the "Tridentine" liturgy. Furthermore, Benedict himself has not (and likely will not) celebrated a pontifical Mass according to the old liturgical books. Furthermore, it seems that on a mainstream parish level, the "Tridentine" liturgy is viewed as either a) an obscure curiosity of a few eclectic groups or b) something more appropriate for memorializing a few limited occasions. If there is any upside for the old liturgy, it is that a commission has been established to determine what methods should be followed for updating the pre-Conciliar Missale Romanum. This being said, it must be noted that the status of this commission and that status of Summorum Pontificum could conceivably be altered by the next pope of Rome. Again, it is all contingent upon how well diffused Benedict's perspective on the old liturgy is within the Roman Church. Certainly, the majority of the laity are unaware and, to be frank, couldn't care less. But all it takes it the right people in the right places, for both well and ill.
Once again, I will not make any claim that this is exhaustive. However, it is a good list for consideration. It is possible that every liturgical mark from Benedict's papacy will carry over into the next. It is equally possible there will be some notable changes, with the status of the "Tridentine" liturgy possibly most in danger of being on the chopping block depending upon who is voted in. Time will tell.