I've obtained an internal memo penned by Activision Publishing president and CEO Mike Griffith that just released to Activision employees at the same time as the press release about the future of Infinity Ward and Call of Duty. It's largely the same as the release that's available in detail here, but there's a key distinction in the internal memo: Activision mentions Infinity Ward's future with Call of Duty.
Even though Infinity Ward studio heads Jason West and Vince Zampella are now confirmed to have left the company, Activision says Infinity Ward is "central to Call of Duty's future."
"Jason West and Vince Zampella are no longer with Infinity Ward," explained Griffith, reiterating what we now publicly know. "Infinity Ward remains central to Call of Duty's future and we rely on the combined talent, expertise and leadership of the team there for its success."
That seems to suggest Infinity Ward is on-board for more Call of Duty. Whether that's Call of Duty: Modern Warfare 3 or something else remains to be seen. Infinity Ward might not even know yet.