George R.R. Martin has posted about the Season 3 renewal, and he adds some interesting information: the number and working title of the episode he’ll be writing for that season, while apparently confirming that it’ll be a 10 episode season:
Like the first two seasons, it will be ten episodes long. This one will cover (roughly) the first half or thereabouts of A STORM OF SWORDS, the third novel in the series.
I’ll be writing the seventh episode, with the working title “Autumn Storms.”