That is incorrect. Go to the Modern Warfare 3 website and look at the bottom of the page 
The founders of IW and a chunk of their staff left the company and Activision to start Respawn Entertainment. IW still exists and is still involved with CoD.
On topic: I used to be the kind of Halo fan that would preorder the game as soon as it was announced, but that was when it was Bungie's game. 343 definitely seems like a dedicated staff that takes the Halo story very seriously, but 343 has no portfolio other than comics, books, and animated shorts. When Microsoft starts stepping up the hype and 343 demonstrates that they're making a solid game, I might get suckered into buying day one, but as of now I'm just waiting.
But I'm more interested in what Bungie's up to than what's going to happen with Halo.
oh, well, let me refrase. what i said.
The
TRUE Infinity ward no longer has control of the call of duty franchise. Now its just all the unimportant people that got left behind from the original, along with Treyarch.

MW3 will fail for one big reason, they have treyarch behind the wheel. Laziest devs ive ever seen when it comes to fixing bugs.glitches/etc.
Even if the true IW was around, it wouldnt matter, COD died after 3. 4 was the breaking point.
On another note, I read the Head Devs devs joined EA to create the team "Martyrdom"