Many people on WoW, WoW forums and on MMO-Champion are convinced that announcing a new expansion this year would be too short of a time between MoP release and NEXT announcement. I am here to tell you that you are indeed wrong, and I have the numbers to prove it.
October 2005: The Burning Crusade
August 2007: Wrath of the Lich King
August 2009: Cataclysm
October 2011: Mists of Pandaria
January 2007: The Burning Crusade
November 2008: Wrath of the Lich King
December 2010: Cataclysm
September 2012: Mists of Pandaria
Time between ANNOUNCEMENT and RELEASE
The Burning Crusade: 16 months
Wrath of the Lich King: 16 months
Cataclysm: 17 months
Mists of Pandaria: 12 months
Average: Around 15 months
Length of Expansions until next RELEASE
TBC > WotLK: 23 months
WotLK > Cata: 26 months
Cata > MoP: 21 months
MoP > NEXT: Around 24 months?
Time Between RELEASE and next ANOUNCEMENT
TBC release > WotLK announcement: 8 months
WotLK release > Cata announcement: 10 months
Cata release > MoP announcement: 11 months
MoP release > Blizzcon 2013: 12-14 months (longest period yet)
With the information above, I am 99% sure that Blizzcon 2013 will reveal the next expansion. In fact, it will not be the shortest peroid between release to announcement, as many believe it would be if something was announced this year. No. It would be the longest.
And just for some side information, NEXT will probably be released OCTOBER 2014.