They will churn them out until it stops working. So far just about every release is a huge spike, even if just temporary, for very very little labor or time sunk into it. It is like getting an expansion release without most the over head. Now do I think Cata is when the downturn will certainly start to happen? Probably a with the odds assessment to say so. I could see interest in MoP again though because it has started to get more a cult following these days as it has aged and "I hate pandas" lost its way. But you never know.. MoP was utterly hated now a lot of people want to play it again. It might happen with more expansions in the future as the distance between them and live increases. It seems to be a thing. Trust me I got no desire to play WoD Classic but I also have no doubt some people might and that might be enough.