Just wanted to say to the people speculating the characters will be from Escape Plan & Carnval Land due to their additions as minions - Chimera & Tag have been added as free minions with the latest update, so that may put that idea to rest.
The stages could still happen. (I really want to see an Escape Plan stage mashed up with Portal. Specifically Portal 2's multiplayer. See P-Body and Atlas messing around with Lil and Laarg would be funny)