Here's a compilation of what was leaked so far(by no means a complete list):
* Dual release on Crysis and Crysis Wars.
* New game mode: Terrain Control
* New maps(made or modified for Terrain control):
Marshes,
Kagoshima,
Thunder rift,
Mirage,
Death Valley * New vehicles:
Hephaestus,
Ares,
Morrigu * New turret types
* Normal ACs wouldn't be overheating, UACs overheat slower
* General weapon rebalance
* Many bugfixes
More possible features(neither confirmed nor disproved by devs):
* New game mode: Free for all.
* New hover:
Epona * New mech(?)
* New battle armor types(?)