back in a Jon chapter in aGoT: "...in his mind's eye he saw ben stark dead, his blood red in the snow. The thought made him sick. What was he becoming?"
I'm not quite sure who the that "he" refers to; is Jon referring to himself or if he's envisioning his uncle becoming a wight?
but then again, jon's not the greenseer of the group.
Jon's not the greenseer of the group, but he may get sent some dreams by one.
That being said: I am not sure Benjen Stark is dead, simply because we haven't seen his body. It would have been easy to stumble across his body during the ranging in CoK and a neat way to finish that story line.
He was vanishing at a very convenient time as well: He wasn't around when all the bad stuff happened to the Stark family; he could neither protect Jon nor compete with him for LC (would have been no competition too ). But if you just need him out of the way, why not kill him neatly?
Since we know that there's more to Benjen joining the NW than meets the eye, I guess his story is not yet done. I was theorizing that his reason is connected to the elopement of Lyanna, namely that he supported it. We know from the accounting of the Harrenhal tournament that he was closest among her brothers to her. That impression is backed by new evidence.
For that reason I also believe that he knows about Jon's parentage even if Ned didn't tell him. Less sure about Jon being legit. Therefore he shouldn't be around when a succession war is going on in the realm.
He won't be Coldhands though, I betcha!