In the second season finale, the former conman (played by Matt Bomer) uncovered a stash of priceless artefacts.
Eastin told TV Line: "The big mystery going into season three is, what's Neal going to do? The idea was, if you give the greatest conman in the world the greatest treasure in the world, what's he going to do with it? Is he going to go the route with Mozzie (Willie Garson) the criminal, or is he going the route with Peter (Tim DeKay) and put on the white hat?"
He added: "We'd softened [Neal] up a little too much [and] got him a little too close to the FBI, so we had the idea to take him back to the bad boy he always has been."
Eastin explained that Neal's loyalties will be called into question throughout the season, but promised that the original culprit of the treasure theft will be revealed "very quickly".
"It just occurred to us... watching all of season two back-to-back, there was one person that had wanted to do a long con all along, who's wanted this forever," he teased.
Eliza Dushku, Jonathan Silverman, Moran Atias, Jayne Atkinson, William Sadler, Anna Chlumsky and Neil Jackson are among the actors confirmed to play guest roles in White Collar's new season.
White Collar returns to USA tonight at 9/8c.
> White Collar, Covert Affairs for crossover?