Whether we want it or not, Sony is developing a script for fourth Men in Black.
Oren Uziel will write the script. He’s also working on a script for the 21 Jump Street sequel.
Men in Black 4 is in the early stages of development, and it is unclear to what extent franchise star Will Smith is involved at this point, though clearly there is interest to capitalize on last year’s movie. MiB 3 grossed a franchise-best $624 million and received warm reviews.
There are no deals for Josh Brolin or Emma Thompson to return, and the movie series is expensive to make for the studio because of backend participation deals with such players as Smith, director Barry Sonnenfeld and executive producer Steven Spielberg.

I thought the third film was going to be the last. While I liked the last film and all, I can’t help but fell they should leave it as is. Its kinda ended, the last film was a good place to leave it at in my opinon.
Ah well, this’ll probably get ’em some nice cash.