Unless Petyr pulls another surprise on us, Jon has Sansa, and Sansa has Jon. If Petyr has any schemes against Jon, and Sansa figures out, Petyr will be more exposed than ever. Petyr's political and manipulative tact comes from the ability of surprise, and that's wasted on Sansa for his attempt to turn her into a pawn. That was his mistake, because if an unknown person kills Jon, Sansa will immediately, paranoid and angry, look towards him with suspicion. As for Jon's other enemies, none of them are witty enough to pull a Red Wedding successfully, and the odds are and have been against Jon so long that he probably lacks any free comfort, so my bet is he'll be on edge up till he has all of the North in order. Even then, though, there are White Walkers coming, so of course we see a familiar type of story here; wherever Jon looks there may be enemies. He's been betrayed before, so his intelligence and attention towards even his closest companions may have risen, and if they have we can expect he'll not be taken by surprise as easily.


Sansa, on the other hand, is still naive in her own way, though so paranoid in fact that she'll never be unguarded enough for a quick kill. Because Jon doesn't know enough about Petyr at this point, thanks to Sansa refraining from informing him, he has no way to suspect him as the reason for any suspicious deaths or plots, and so Sansa is the only one in the North who has valid information against him. Thanks to that, if Sansa were to die, Petyr would be back in a game where he has nothing to fear.