I agree. I thought they would annualize CoD XP, to be honest. It was thoroughly successful last year. Perhaps it's a matter of Treyarch wanting to do as much as they can with the time they have left before officially revealing anything too grand. Perhaps, like you said, it's a financial thing. I suspect that they won't stop it all together though.
My prediction is; depending on how far IW/SH are willing to go next year, if they take as many or less risks than Treyarch, then we'll see another XP.
I imagine they think that BOII will be drastically different, and they want that to be evident in the reactions all at once instead of letting people see everything early and diluting the anticipation and excitement. And possibly losing sales because of the jaded and cynical that don't buy it because they think it's not enough change.
Though I suppose you can't please everyone. :]