If handled properly, this could be a massive cash cow and something I'd potentially try. The current structure of the CoD series' multiplayer isn't very different from something like Blacklight or Alliance of Valiant Arms, so a F2P installment would be a pretty natural extension of what Treyarch, Infinity Ward, and their little buddies are already doing.
Knowing the Chinese MMO market, it's clear why Activision wouldn't bother to bring it over to the west other than the god knows how many millions deal they have made. The market in China has a total pay to win culture. The general public who are into MMOs there generally believes that paying to have gameplay advantages over non paying players is a rule. It's better off to stay away from it unless you're into that kind of stuff.