Done wetting your pants little kiddies? According to a post on anime blog Canned Dogs, an announcement in Newtype (the Japanese one) says that new information about the second season of Haruhi Suzumiya will be released in the July issue of the same magazine.
Also, as reported by an SOS-Dan forums poster, the official Haruhi fan club has confirmation that the new season will be based on The Disappearance of Haruhi Suzumiya, the fourth novel in the series. News will be released as it comes.
EDIT 1: Early scans of the Newtype July issue have been released on 2chan. They can be found here. The magazine will be on sale June 10th in Japan, so we can expect the article to be translated that week.