In the books, there's more than zero reason to think that Jon might return from Ghost into some other body. I always thought it'd be fun if he returned into Stannis's body or something. Would make it easier for him to leave the Watch, although coming back from the dead might be enough to accomplish that anyway. But in the show you gotta figure that if (lol) Jon returns, it will be into his own body, if just for the continuity with the actor and all.
In the show, he's dead for sure.
how do we know if stannis is really dead?
In the show, he's dead for sure.