If we weren't spoiled about Jon Snow's fate, then the writers could've taken as much or as little time as they liked to draw out his comeback and it would still have been a shock. Now the cat's out of the bag, the writers must surely work fast to bring back Jon as soon as possible. If they don't, it will be a tedious wait for the comeback and could overshadow a potentially brilliant season. Jon needs to return in the season premiere if his death is to avoid becoming a farce. It needs to be handled extremely well, but speed is the key with the entire audience already aware that a comeback appears to be on the cards.