CEO John Smedley teased the announcement on his Twitter feed last night, saying that the game is pretty far along. "You can play it yourself soon," he tweeted. "And by play I mean fully."
The game's website has also gone live, though it's currently a single image.
[Smedley has since confirmed that the game is indeed zombies. "H1Z1 is an MMO that allows players to take on the role of an apocalypse survivor who is in a world that is filled with zombies [... ] A world! Not just a little tiny server."]