It's been a little while since the last news. As previously related, HBO completed filming of the pilot for Game of Thrones in late November 2009. The pilot has been undergoing post-production since then, with news emerging that HBO are planning to make a formal announcement on the project being picked up or not by the end of March 2010.
At the Television Critic Association press tour today, HBO were full of news and announcements regarding their big 2010 shows, namely the returning True Blood, new ongoing series Treme and Boardwalk Empire, and the major mini-series event The Pacific (the follow-up to Band of Brothers). They also let slip a tidbit about Game of Thrones, revealing that they expect the completed pilot to be delivered in two weeks (around the end of January/start of February). If they really like the pilot it's not impossible that there will be an earlier decision to pick up the show. However, quite a few sources seem adamant that the news, positive or negative, will not be announced before March.
If they do pick up the show, it is likely that production will resume in the late spring or summer. We already know that the production will last for 30 weeks, taking us up to the end of the year, making a spring or early 2011 air date quite likely. However, it's worth reiterating at this point that the series has not been picked up yet and although the vibes are positive, it isn't in the bag yet.
Update update: The Hollywood Reporter is now reporting that, according to HBO, the series they've seen so far 'looks fantastic' and that, barring a catastrophe, the series will be picked up in March for a March or April 2011 premiere. It's still not the final green light, but a huge statement of confidence in the show.