Here are the hints, clues, and suggestions for the upcoming season!
Re: The Troubled. Remember the Chameleon from Season 1, Episode 9? The writers say: "We're not done with that one." Might the shapeshifter reappear in the next season? Has one been around this entire time?
Re: Dwight: The writers were blown away with Adam Copeland's performance, both in auditions and on the actual show. They're aware that Dwight is a fan favorite and they're eager to work with him again--but at the time of the panel, they'd heard about the season 3 renewal some 24 hours prior.
Re: Nathan's tattoo! This is a potential spoiler, but Lucas Bryant explained that when Nathan got the tattoo we saw in the Season 2 finale... he felt it. I wasn't sure how seriously to take this (Lucas Bryant is a jokester par excellence) but Eric Balfour seemed to think it was legit, since he mentioned the info's spoiler potential and applied to it a verbal hashtag "Epic Fail."
More shirtless Duke and/or Nathan! OK, this one's mostly a joke, but you're welcome to dream. Eric Balfour: "I actually get to help take his shirt off..."
More Nathan in general. The writers say that Duke was their envelope to open in S2, and that Nathan's going to be the focus in season 3. Rejoice, pancake fans!
Other stuff I didn't know about Haven's writers: They've got a 15-page series Bible detailing the show's mythology, and they already know the last scene of the series.
Can't wait for season three, although we're probably going to have to wait until next summer to see it!