Activision likes money. Can you confidently say that somehow they'd make more by making map packs free? Somehow I doubt that if they only charged for cosmetic items, or whatever most F2P games do, they'd make more money.
Easily, I listed six games that are doing exactly that.
And if you think F2P games aren't making money... let's just say that's exceedingly inaccurate.
And I forgot GW2, another ideal example of that model, but there are many others. High quality core content, continuous updates, and a healthy market mean both good revenue and the ability to push updates to the larger non playing populace, who keep the overall population level and interest in the game high.
World of Tanks is also particularly noticable, that game is insanely big, but it hasn't picked up a ton of traction in the west yet. That MWO is copying so much of what it did directly is a testament to how well it is working.
http://www.gamesindustry.biz/articl...monthly-profits-hitting-double-digit-millions
http://www.gamesindustry.biz/articles/2012-06-11-wargaming-net-revenue-will-triple-within-a-year
Oh and Firefall. Hell, there's tons out there. Many of Nexon's games function on that same sort of economy.
But the more directly comparable FPS or action oriented games are also doing either well or extremely well, depending on the particular game. I seriously doubt if there will be significant barriers in the way of such payment structures on the next gen consoles, and we already have games with hilariously awful DLC schemes that far outprice the base game - the better F2P games have much better ideas for how to handle that.