What's in a name?
The iOS COD games are shit. The Assassins Creed game for PSP isn't highly regarded...Activision Is going to be protective of their cash cow, where it counts: console.
The Vita doesn't have the clout/market share for them to invest heavily in the platform. My guess is whatever iteration the handheld is receiving, is on Sony's dime.
Seeing how Sony bungled the Vita Resistance (their own first party fps, the first with dual sticks) iteration - my hopes aren't high for COD.
I didn't mean COD as in quality actually