It appears Call of Duty may finally shed its aging engine. If so, Black Ops 2 will be the last game to use the IW engine, which has its roots in id Tech 3. Based on the resume of an Infinity Ward engineer, Activision's other Call of Duty studio is working on a "new high-end DX11 code base."
The resume of Andrew Aye shows work on an "unannounced title" due for PS3, Xbox 360, PC DX11, and "TBA." Given that the current slate of consoles cannot run DirectX 11, it seems likely that "TBA" represents an upcoming next-gen console.
Kotaku points out that the next Call of Duty game may see a multi-generation release, a la Call of Duty 2 where "current-gen versions are ported down from their cutting-edge counterparts."