I love Blizzard's timing... by setting a date we can surmise that WoW's Free-to-Play model is failing and that May 15 is the latest date that a release-date-averse publisher like Blizzard feels it can still preempt the Guild Wars 2 release. It makes one wonder if these large publishers have game theoreticians working on optimum release dates.
There definitely have to be some solid reasons behind this specific release date given the fact that they've been cutting features in the last couple of months to be ready to ship in May (such as PVP). When were their other games launched? I seem to remember StarCraft 2 launching around May/June.
(Hopefully unnecessary disclaimer: I work on Guild Wars 2.)
SC2 was released early July 2010. D2 was released in late June 2000. WoW and its expansions in successive Christmas seasons. So, yes, I'd say that May 15 is atypically early for Blizzard. Given the online auction house component, they may feel that it's necessary to hook the summer crowd early to maximize returns from that casino.
I wouldn't be surprised if this move forced Arena Net to push back to a Thanksgiving release, since people generally don't play two online "collect-em-all" games at once.
WOW is definitely heading into its twilight. If I was a betting man, I'd say MOP is the last expansion they'll put a lot of resources behind before throwing everything at Titan.
