It's a common thing in other MMOs for the studio to boost experience gains (usually by 100%) for a weekend here and there. It gets lapsed players back into the game, gives current players a reason to dust off old alts, and repopulates the non-end-game zones like nothing else. It even has a little bit of a long lasting effect in that players will likely continue to level their characters they got a leg up on via the XP boost, and that creates more overall engagement; which is the critical factor for any MMO.
Blizzard has ventured into this area now with Diablo III. We're all getting 50% increased experience until Reaper of Souls comes out on March 25th. It's a really great time to level your alts. Personally I'm planning on getting my monk up to 60 before then (I'm a big fan of flashing around and stabbing baddies). From my completely unscientific poll of everyone on my Battle.net friend's list, nearly everyone is playing Diablo again. The XP boost seems to be working.
But what about WoW? In some ways I don't want to see it, I have a gut feeling that it's a sign that the game isn't doing well, that Blizzard needs to attract players back to the game. But in another way I feel that if this is the way the market is moving overall, then why shouldn't WoW do the same? And at that point, wouldn't it be irresponsible of Blizzard not to offer the same level of service to WoW players as they can get with other titles?
My bet? It's coming to WoW a month before Warlords of Draenor releases. What do you think? Let us know.