I've always hoped he come out with a new Zombie Mod. It's so much fun, but could use improvement.
I remember way back before the shadows and shaders were announced and people were still talking about Rotondo's zombies, someone mentioned he was waiting for another version because it would affect the mod. Then we got the Blockland Launcher a while afterwards.
Then jump to the future, we get the shadows and shaders update. Which also happens to have an update on gamemodes and minigames.
We've learned from Wedge that there is a hidden board only some are allowed to see where they talk about future updates, but he didn't want to tell us any more about this since some of the things might never happen and they are really far down the road and stuff. Regardless, we know updates are talked about on this forum. And we know that Rotondo has been waiting for a certain update until he updates Gamemode Zombie.
Maybe v21's gamemode update was it. We just have to wait and see.