According to Activision Publishing CEO Eric Hirshberg the next iteration of the series, Call of Duty: Ghosts, is to get an engine upgrade. "Infinity Ward set the gold standard for first-person action for a generation, and they're going to do it again with Call of Duty: Ghosts."
"Ghosts delivers an all-new story, all-new characters, an all-new Call of Duty world, all powered by a next generation Call of Duty engine, which is a leap forward for the franchise. Infinity Ward is going all-in to create the next generation of Call of Duty worthy of the world's greatest fans."
Whether this means that the IW engine will be getting a massive overhaul or if the IW team are outsourcing the engine remains to be seen. Either way,
I totally called it we caught hints of this last year, so it isn't much of a surprise.