We're already well into that "en masse" movement I think--it's just been happening on an individual basis under the radar, with very few actual bodies/parishes coming over ala the Anglican Use parishes. The TAC merger may turn out to be the the high-water mark, because from what little I know, I don't think too many other Anglican bodies are as Rome-inclined as the TAC has been. The low-churchers and broad-churchers certainly won't make the trip.
However, I think it is true that if TAC comes in and is granted some sort of Apostolic administration or other arrangement that allows a distinct Anglican patrimony to exist under Rome's jurisdiction, that may inspire even more Anglo-Catholics to come in on an individual/parish basis, and perhaps some of the people that already came in (e.g. Al Kimel, Bishop Steenson) will gradually migrate over to that new structure.
The reunion of the TAC under an appropriate juridical arrangement is what we are hoping and praying for down here in the Anglican Usage of the Roman Rite, I can assure you. The Anglican tradition, in its Anglo-Catholic variety, brings a lot of old Catholic material, especially the collects, back to the Church at this great time of true renewal of the Church in continuity with, not rupture from, her 2,000-year history and practice.