After Game of Thrones posted spectacular ratings in its premiere episode for its second season (see "'Game of Thrones' Opener Sets Records"), and posted an even more spectacular 97% hold of that premiere audience for the second episode of the new season (see "'Game of Thrones' Posts Remarkable Ratings Hold"), it appeared, as ICv2 speculated, that a renewal for a third season was only a formality. 

According to Deadline, HBO surrendered to the obvious today and renewed the series, praising series creators David Benioff (X-Men Origins: Wolverine) and D.B. Weiss for “raising our expectations for a second season, and then surpassing them.”

With comics (from Dynamite Entertainment), board and card games (from Fantasy Flight Games), and an RPG from Green Ronin (see "'A Game of Thrones Edition' RPG"), the HBO series is a key media sales driver of a series of major geek culture products, to say nothing of its importance in demonstrating the continuing viability of epic fantasy as a key TV and film genre.