Yearly expansions are their ultimate timetable goal. That's all they've ever said. No promises, not even a statement that its even possible currently.
And honestly, they could. But they won't compromise on quality, since that's the main thing keeping WoW going after all this time. And anyone who disagrees probably does so for a trivial reason.
Even 18 month expansions would be interesting. Especially if they keep up the 6 month tier timetable and give us three tiers per expansion. That would keep me reasonably happy. But I won't expect it, because I know how hard it is to keep to timetables.
Also I suspect they are already working on the next expansion. Planning, concept art, story, etc.
And WoD's beta won't be as long as MoP's. No talent overhauls, no new class or specs, no testing out Flex. That cuts down on huge amounts of work, and also cuts down the amount of player feedback required - thus more testing can be done internally.
Heck, WoD could probably be launched without an open beta at all. But I doubt they'd do that.
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Uh huh. So how many mounts are in the store right now? Still only counting 7. That's nothing to cry over non-stop about.
They stated that a Beta is crucial and extremely necessary. But I agree with you that the amount of WoD testing is going to be much less than MoP, with no major changes really being implemented. Garrisons are really the only thing that comes to mind, PvP will be relatively stable considering the lack of a new Class. Flex technology is being "tested" by SoO as we speak, and Mythic just means they only have to balance one difficulty of hardcore raiding instead of 2.
Consider the fact that they increased the WoW team by 80%, I don't think its hard to believe that they are now capable of increasing their output by 80% as well. That means either faster expansions with equal content, or equal duration with more content. They've made it pretty clear that they are shooting for the former.