WOW works because it's pure uncut heroin. You get hooked, you wake up and your fired from your job, your girl left you, and you can't make rent but you don't care

COD series is addictive, but there's currently no incentive anywhere near that level. They would have to change the way they think of things, perhaps go in a Planetside/Mag type way.

Overall, considering how well the game sells as is, if they were smart they would just focus on raping the audience with MAP packs