I looked at the wikipedia page and it says something about Sledgehammer working on a new game. Could be a spin off or something? Guess we'll have to wait and see, but I hope it's Treyarch. I really liked the direction and imporvements they made with Blops.
A new engine would be great. CoD really needs to evolve. I think they should have more varied gameplay in the multiplayer. There's a level of MW3 in a sandstorm - how cool would it be if they made a multiplayer map like that? Or a night map, where you could seitch nitghtvision on? Or one set in a jungle, not like Blops jungle I mean one with no buildngs or roads? Or an underwater research base thing, with windows and glass walls in places so you can see fish swimming by.
The maps they've been coming out with are generally good individually, but if you take them as a whole, they're just too samey. The gameplay is much the same on all of them. Maybe you hide behind an upturned car, instead of a table, but it's nothing more than a cosmetic change.
EDIT: another cool map idea - aircraft carrier. You can fall off the sides into the sea and drown
EDIT 2: they should have interactive maps like what Treyarch started doing in Blops. For example on the aircraft carrier you could activate the aircraft deck lift, etc etc. In the underwater base, you could shoot certain bits of glass which would flood sections. The enemy could then activate a pump to unflood them.