It's too hard to predict. But off of research this is what we know.
343 Industries - 2 team studio - Concurrent development of Halo 5 and co-development of Halo Anniversary)
LA Studio - Next generation core cinematic title
Connected Experiences - Untitled Project – Design Large scale multiplayer title and help other first party studios
Rare - 3 team studio - Concurrent development of various titles. Likely working on a racing game as well as a new IP.
Platform Next Studio - Next generation core title
Twisted Pixel - 2 team studio - Concurrent development
Lionhead - Unannounced MMO-like New IP - (2 team studio - Concurrent development unannounced next generation title)
Victoria Studio - Untitled Project (Literally nothing is known about them yet as far as i am aware.
Black Tusk Studio - Next Big title in terms of quality is compared to Halo
Press Play - Nothing is know about them yet
Lift London – Multiple Cloud Based gaming projects
There is also other studios but they are dedicated to Kinect or mobile games so i didnt list them.
