The way Will offers what some might seem an excess of information, combined with the minor lack of social graces and the dislike of both eye contact and social interaction does make Hannibal lean towards the idea that Will is somewhere on the spectrum.
But more interesting than that is his empathy. His ability to look at something from someone else's point of view. "Tell me, Will. In your dreams, the nasty ones, do you ever take the place of someone you've read about?"