Either way, this studio is dead...
Not entirely.
My guess is that they were paid their 2009 bonus already, but it didn't include the year-end sales as accounting wasn't complete on it.
Regardless, a certain percentage of people are going to leave the studio. I'd also guess this is a devastating amount. However, some will stay. Why? Because it's the studio in charge of the #1 franchise out there and there are suddenly huge leadership gaps. It's a chance for people that had been a few rungs down the chain of command to get instant promotions and have very clear influence on the way the game and studio go. For some this opportunity will be impossible to pass down. For many, many others, that type of responsibility is a hassle and they just want to go somewhere to make fun games with fun people.
Within 2 or 3 years we'll be hearing about some new, awesome FPS franchise from an unknown studio shortly before finding out that it's made from the majority, if not all of the people from IW.
I'd be curious to see how IW's mindshare does without the CD:MW label. To be honest, they caught lightning in a bottle there. Right game, right time. I think even the most diehard fans admit there are serious flaws. The plot makes no sense and is very poorly delivered (very), AI is wonky, death comes too often with people often forced to repeat the same 30 second part of the game over a dozen times due to fluke bullets, enemies infinitely respawn, etc. There are many, many shoddy decisions in the game. Fortunately there were many very, very good ones, almost all centered in multiplayer.
I think, right now, there's a huge amount of questioning in the industry over whether the fans will follow the IP, the developer, or neither. Where are the loyalties? Will a non-Bungie Halo game sell as well? Will a non-Halo Bungie game sell well (I'd guess yes, Bungie has done a masterful job of branding themselves.) Will a non-GoW Epic game dominate? Same here. If you take MW from IW do they still break 5 million units sold? With WoW they've got some evidence that title is enough to sell, but I wouldn't call it great evidence. Beyond this, I'm a firm believer that title is a huge influence. Give a game a great name and it'll sell. Give it a bad one and it'll die.
It's interesting, though. Of the controllable, what's most important:
-Quality
-Pedigree
-Legacy
-Title
-Marketing