Rereading ASOIAF, I find a great deal of foreshadowing of events. I think I may have found one in Tyrion's second chapter of AGOT.
"The wolfswood," Benjen Stark called it, and indeed their nights came alive with howls of distant packs, and some not so distant. Jon Snow's albino direwolf pricked up his ears at the nightly howling, but never raised his own voice in reply.
Mayhaps it's oversimplistic, but does this mean Jon will never play any part of the Game of Thrones? Robb went to war, Jon stayed on the Wall. Eddard was murdered, Jon stayed on the Wall. Theon took Winterfell and "murdered" Bran and Rickon, yet Jon stayed on the Wall. Soon "Arya" will return to Winterfell and set the Bolton's upon the Stark throne, will Jon stay on the Wall? Ultimately Dany will invade and mayhaps Jon's Targaryen heritage will be revealed, will Jon stay on the Wall? Will he never raise his own voice to be like the pack?
Couple this with Aemon's life and example... and mayhaps Jon may never leave the Wall.