That’s a pipe dream and a half.
Introducing the tree all at once was necessary as it needed to change them all at once, but if they increase each tree to 4 or 5 branches (So 4-8 new branches in total for current archetypes), they probably will lean toward doing it like they did the careers in VT2, where every year they released 1 (Well 1 year at minimum, some took quite longer).
Seeing as a branch in theory take less time than making a full career, I would say that 2 branches a year (So likely starting with Veteran, and either Psyker or Ogryn; Then the year after doing Zealot and the unpicked one) would be more appropriate.
As for Archetype, there is still the major problem on how it’s monetized, where it’s clearly dlc level content, but at the same time they may wish to be able to treat it as a base game content, for additional weapons, but also for cosmetics, where selling dlc for dlc does cause problems on the Microsoft side.
We’re seeing the end of year 2, new branches could be returning to the table at the end of year 3, but archetype is very much year 5+ considering FS’s speed.
6 Voice actors and the number of voice lines alone would be such a big ordeal.