Director Gullermo del Toro spoiled any hopes of his two-part adaptation of THE HOBBIT getting the 3-D treatment about six months ago, but he's begun to sing a different tune in a post at THEONERING.NET [1].
His latest post reads: "I wouldn't read much on it just yet, but now, after all this time, after AVATAR doing the Box Office it did, we have had [enquiries] from above about The Hobbit being in 3-D. No impositions or heavy leaning. Just [enquiries]. Just fulfilling my promise to let you all know if discussions ever started."
The first part of THE HOBBIT is officially schedule for release in December 2011, but recent reports push that deadline back at least a year, which would warrant the timeframe needed to bring the film into 3-D.
Links:
[1] http://newboards.theonering.net/forum/gforum/perl/gforum.cgi?post=241750;guest=10392680#241750