I would bet my bottom dollar on Team 3D remaining with TNA. With the EV2.0 storyline in full swing and their histories with many of the guys involved in this angle, it would seem logical that they would remain in affiliation with TNA wrestling.
I don't really know where else they would go or what else they would do. I know by pro wrestling standards, they are getting up there in age, but they aren't really that old and may not be ready to retire yet. I doubt WWE would be an option for them. I think they've burned too many bridges with Vince McMahon along the way and even if they wanted to return, I doubt it's a viable option. They likely don't want to go to ROH, or Japan, or Mexico, or anything like this at this stage of their careers. I guess they could be backstage guys/road agents or something like that, but otherwise I see TNA as their only realistic option.
They seem well suited to TNA's current angle anyway. Getting older, out of shape, not as talented as they were in the past, less relevant than ever, seems like a marriage made in heaven to stay exactly where they are at the moment, and help further the EV2.0/Fourtune rivalry.