Update: the official release with casting information is now posted.
I haven't seen the details yet or the press release, but according to the BravoPR twitter account Top Chef has been renewed for a seventh season:
BravoPR Bravo Picks Up Season 7 of "Top Chef," Launches Nationwide Casting Calls
Hardly a surprise, but still happy news for fans of the show. We'll post the details as soon as we see them.