Like you said, pretty obvious for those that have been around for a while...
Since when is September the holiday season? October and the beginning of November aren't even the holiday season.Wotlk, Cata, and MoP betas took 6~months. You're suggesting that they will release an expansion in the Summer season instead of Holiday? And that's less ridiculous than my idea?
It happens every time an expansion is getting close to being announced, a bunch of people get on and start coming up with crazy ideas about when the next one will come out and why it will be way off from what should be expected. Then they are miserably wrong.
The formula is simple really. Take the known facts in to account, such as known last raid tier, Blizzards statements, etc. Then add a month or two on to that for delays.
So, last raid tier of MoP being released around sep-oct.
Blizzard statement of getting content out much quicker, and proving it means the last raid tier will only last about 6 months, which brings us to March or April.
Then the last step of adding a month or two on for delays leaves us at approximately May 26, 2013 at 12:00AM.
Sorry, but this is the most hilarious thing I have ever read.