The official announcement (https://www.crytek.com/news/crytek-is-pleased-to-confirm-a-new-crysis-game-is-in-development) post really label it as Crysis 4 but it confirm Crytek is working on a new Crysis game. This has been suspected considering the recent remasters for the original Crysis trilogy.
According to the announcement post, the next Crysis game is in the early stages of development but the team wanted to let us know it’s in the works now. Crytek states they will be releasing more details as development of the new game progresses. The developer also added that they have news coming for Hunt: Showdown too.
While Crytek didn’t call it Crysis 4 in the announcement post, the announcement video does. The short teaser uploaded to YouTube doesn’t tell us anything about the game but it does confirm that Crysis 4 is only working title still. The title of the game will be confirmed in the future.