MW3 is little more than a copy and paste of MW2. Had Jason and Vince and the other 50 or so employees of Infinity Ward not been fired or left, then MW3 would have ended up being a far more innovative and probably better game than it is. Since such a huge chunk of Infinity Ward's best talent vanished Activision had to completely reconstruct the studio, and they also had to call in extra help from another studio called Sledgehammer. Its obvious these guys don't have the same talent or genius, because MW3 frankly isn't that innovative or great. The scrubs they called in to create MW3 obviously didn't have a clue what they were doing and they were in over their heads... the only reason MW3 wasn't a total flop was again because they copy and pasted MW2 over, then made a few tweaks and called it a day.
That said, I don't have high hopes for MW4 (or whatever the next Infinity Ward offering will be). The studio is gutted of its talent and even though the name may be the same, its not the same..... You could compare the current Infinity Ward with the current Rare, because the situation with Rare is very similar. Rare was once an excellent studio full of talent and genius, but now that all that is gone its just an empty husk.
At least Activision still has Treyarch, and for that reason I think the COD franchise still has a bright future, but every odd year from 2011 forward its going to introduce a game which is an absolute turd. Only in the even numbered years will there be a COD game that is awesome. Fortunately this year is an even numbered year which means a Treyarch game is coming (Black Ops 2).