Zack Snyder is clearly not finished with the Army Of The Dead universe. A prequel (more details on that one here) is already on the way alongside an anime spin-off series, and he's also now developing a film sequel.
It's all part of a big new deal that Snyder and producing partner/wife Deborah Snyder have signed with Dead host Netflix, which will see their The Stone Quarry Productions making all manner of projects for the streaming service. Buried in a Hollywood Reporter story on the deal is a mention of Snyder working on a Dead sequel with co-writer Shay Hatten.
The Dead sequel will have to get in line, though, as Snyder's next gig is sci-fi adventure Rebel Moon, which is also part of the Netflix contract, and should be in production early next year. Get the info on that one right here.