I had heard BuddyTV was at the con and they managed to grab some time with Jamie. The interview can be found HERE. An mp3 of the interview is also available to listen to. He talks in very general terms about Season 4 and I saw nothing that I would deem a spoiler.
The most interesting thing to me is that he said he didn't know what he was doing next. Mineville doesn't begin shooting until the fall so maybe he's referring to down time in between.
ETA: meshel73 has converted the mp3 for download. She's provided a link in comments. Tell her how much you love her. ;)