Activision finally confirmed the rumors late this afternoon/early evening. Jason West and Vince Zampella have both been let go from the developer. No official reason has been cited by Activision yet, but we do know that Activision filed a Form 10-K Monday with the SEC, citing breaches of contract and insubordination.
Many are now speculating the reasons, with various theories out there. One of the biggest deals with creativity, stating that Infinity Ward wanted to step away from Call of Duty and start a new franchise. As we all know Activision is all about milking a franchise on a yearly basis, so they could have viewed this as a threat to sales. It's no secret the best Call of Duty games came from Infinity Ward.
Many in the industry have begun to comment on this, with the best quotes being from Tim Schafer (Psychonauts, Brutal Legend), "Getting mad at Activision for this kind of thing is like getting mad at an ape for throwing feces. It's just how the beast communicates." on his Twitter account, and also Alan Kertz (Senior Designer on Battlefield: Bad Company 2), "IW falling apart? Way to go "Activision, you just shot your cash cow. Dumbasses. Respect for those at IW if true.", also from Twitter.
Time will tell as to what the reasons were specifically, but you can be sure we will report on them as we find out more details. Our best wishes go out to all affected by this now and in the future.