Westeros wasn't quite as interesting to Bethesda as Skyrim was.
Bethesda's Todd Howard says that the studio was approached to make a Game of Thrones game, but turned it down. Howard says that there was a lot of interest internally about making a game based on George RR Martin's A Song of Ice and Fire books, but ultimately Bethesda decided it wanted to spend its time differently.
"With A Song of Ice and Fire, we went 'We want to do that!'" said Howard. "People in our studio liked it, and it seeped in a bit to what we were doing ... We wanted to do our own world ... Before we were even making Skyrim, there was a conversation with George R.R. Martin's people. They thought it would be a good match - and so did we, actually - but then we thought about if that was where we wanted to spend our time. It was tempting, though."
Howard's comments make it sound like Bethesda has shut the door on working on the Game of Thrones franchise for good. If that is the case, it's rather a shame, because - as Howard says - it would have been a good match. Still, there's no harm in keeping your fingers crossed, even if it is just wishful thinking. Don't worry if you can't wait for this nebulous future time that may or may not come to pass though; the books have still been made into a game, just not an RPG. Cyanide Games has created an RTS called Game of Thrones: Genesis, which comes out on September 29th.
The Elder Scrolls V: Skyrim, also known as the game that Bethesda made instead of Game of Thrones, comes out for PC, PS3, and Xbox 360 on November 11th.