That's my thoughts exactly.Ned's dream where he remembered his sister on her deathbed, covered in blood, possibly from giving birth to Jon. Her final words, "Promise me, Ned." I read that to mean her wanting Ned to promise to take care of her son. I think the father is of dragon's blood--not the Mad King, so that leaves only one candidate.
The only possible living person who would know is the frog eater who accompanied Ned.
Agreed.
Well, that particular promise - the exact content of which has never been revealed - seems to have haunted (and guided) Ned for the rest of his life. Again, I'd be most surprised if it didn't in some way concern Jon. And, given that, I would be further surprised if some strange other-worldly device did not return Jon in some way for his tryst with destiny later in the series.
Neither Jon's backstory nor his future (unlike every other character - the ones killed invariably had a full backstory) have been sketched in more than the merest of detail, a strange omission for a character to whom so much space and so much emotional investment has been made.
I expect to see more of him in some capacity.