Rumours are there will be a Crysis 4 depending upon the overall reception to this Crysis trilogy. They first tested the waters with the Crysis 1 remastered. It sold okay enough to green light the 2 and 3 remasters and they put much more effort here so that it sells even more. If it sells enough, Crysis 4 is supposed to be green lit. Since they are strapped for cash at the moment, it’s also why the game is only on Epic so they get more cut of the sales.
Afaik the only thing we know about the next Crysis is that it was planned to be a battle royale of sorts, this from when Crytek got hacked. Crysis 3 did meh sales numbers overall & they just gave up on single-player experiences being viable financially. Most of their money comes from Warface, which is PvP selling mtx, and Hunt, which is PvPvE, and to a lesser extent some VR work. So I'd be surprised if they do a Crysis 4 in the spirit of the trilogy.