Honestly as much as I love the crossing the streams being bad stuff in the first film, in a game, that might prove more annoying than anything. Just from the videos I've seen, if you're in the middle of a free for all with a bunch of ghosts, it might be bothersome to have to worry about crossing the streams AND catching ghosts… and even MORE bothersome to game over because of it (I mean, you're near the end of a level and there's a ghost. You and the AI or another player blast at it at the same time then all of the sudden all life as you know it stops instantaneously and every molecule in your body explodes at the speed of light. A fun game that would not make).
I dunno. Personally, this is what I hope happens: