Bog fairy

If Jon really is the son of Rhaegar and Lyanna, and if he truly is the "prince that was promised" as many out there say, then why was he stabbed to death at the end of the last book? I'm not referring to the TV series. If he doesn't come back from the dead, it would seem all a waste of time. If he wasn't dead, just wounded and unconscious then that could be better than making him a wight. If he's alive or undead as a zombie in the future books, will he ever meet Lady Stoneheart?