The best thing that came out of Call of Duty: World at War was its zombie mode, that was then trumped by Black Ops's addition of dead presidents. Black Ops 2's change to the formula looks like it could be quite substantial, if the latest teaser trailer is anything to go by.
So, what have we got to go on? The music is a simple piano version of 'Ring a Ring o' Roses' - appropriate for a mode about a zombie plague - and a bus. Are you driving zombies to school? It would be a sea change to the game but not necessarily an unwelcome one. If anything, those closing shots of the zombies running after the bus, and trying to claw their way in would seem to confirm the zombie school bus theory. I can't tell you how many times I've seen people run after buses in movies. It's the done thing.
It may also suggest, but this is much less likely, a campaign similar to Left 4 Dead's. Where each level is you trying to get from one point to another. Yeah, like that's the case.
Guess we'll find out on the September 26.