I continue to watch this project with much interest.
Sadly, there does not appear to be much of an update to report. Angelus Press did a fair job at giving people a behind the scenes peek at the publication of their 1962 Missale Romanum. At present, it appears the interest in a Pre-1955 Missale Romanum is too esoteric to warrant such an expose. This state of affairs should be expected. There appears to be almost no room to consider editions of the Roman Missal prior to 1962 - the Traditionalist world just isn't wide enough, apparently.
There are criticisms one can make of the publisher's choices here. There is an argument to be made that the what we could reasonably call the "ancient Roman Rite" was no longer in force by 1950 or so with the changes to the Mass of the Assumption, which up to that point had an established history in addition to thematic affinity to the tradition of the Dormition in the East. This, mind you, is not the only reason for such argumentation. Persons fair more familiar with the subject matter can provide a pretty thorough list.
This being noted, I would like to see the publisher's endeavor take off. The only way to really launch a movement of rediscovery of the pre-modern Roman liturgy is to publish an edition of the Missale Romanum before the reforms of Pius XII. This is not to raise call to displace 1962, or 1970 for that matter. Rather, it is a conviction that the pre-modern Roman liturgy constitutes an accessible avenue for exploring the historic Tradition of the Western Church and, in many areas, reflects an earlier epoch (in thematic affinity if not in actual use) in Christian history. As such, it ought to be preserved, studied, and, God willing, practiced.
Currently, there is no other comparable publication effort for any earlier edition of the Missale Romanum. I suspect that should this effort fail, the next attempt will be a long time coming.
If anyone is interested in the Roman liturgy pre-1962, or pre-1955 for that matter, The Tridentine Rite blog is well worth your time. The author's aim is clear: demonstrate via actual contents what a liturgy according to the liturgical books as promulgate Pius V would look like (when celebrated without the subsequent changes).