According to the director there’s already a clear idea of when part three should happen.
Ruben Fleischer, who is currently promoting Now You See Me: Now You Don’t, has of course not forgotten Zombieland, and the last time we saw Tallahassee, Columbus, Wichita, and Little Rock was in 2019’s Zombieland: Double Tap. If Fleischer gets his way, there will be a third film, and he also knows when he wants it to happen.