According to Scriptflags the release of both parts of the prequel have been pushed back:
“Ridley Scott’s Alien Prequel #1 & #2 have both been pushed back a full twelve months to 2013 & 2014. There has been no official explanation from Fox or Scott’s camp. This comes two months after their first publicized fallout over budgetary and rating criteria.”
The article doesn’t state any sources however. Thanks to Shasvre for the news.