Everyone QQ'ing about how MW3 will be the same needs to realize something:
Games don't need to constantly change what they are to be good. If MW3 is an expansion of MW2, than fine, because MW2 was fun as shit to play. This means, that by extension, MW3 will be fun as shit to play too.
I don't think I need to bring up instances like Killzone 1 vs Killzone 2, where Killzone 1 was fucking amazing, then they decided to change everything around in KZ 2 and the game was boring. Use your brains people. If one game is awesome, and they release a very very similar game, chances are, the second one will be awesome as well.
The only problem I see it the price tag. We all know it will be $60 a pop, which IS really expensive for something that's pretty much a really big expansion. I could see $40 or maybe $50, but that's a little high.