Infinity Ward isn't really "pushing" anything. I'm sure the campaign will be as "cinematic" and fun as the last one, and it might not have the problem of endlessly respawning enemies that made the better option for a good part of the game to hold the shift key and ignore enemies, but it sure isn't pushing anything. However, if it allowed you to kill children, then I could probably accept and love it for "pushing boundries" and by that I mean make it superior than any game that has children in it that just absorb and completely ignore bullets (yes, I'm saying the game could be better than Fallout 3 if it let me kill children in preferrably graphic ways, yes I'm just being spiteful because of Little Lamplight, and YES, this is old news, and no, I probably didn't need to say yes in all caps).
I didn't much care for the multiplayer of Call of Duty anyway, and I'm not quite sure why it's so well liked. I, for one, would much rather play Battlefield 2 if I want a game in a similar style. I admit did appreciate the removal of any sort of HUD, and would like to see this in other games, but other than that it really doesn't have that much going for it.