I used to joke that he would come back because i really didn't think he would
But now... few things happened:
1 - He keeps on saying he'll comeback. Yes, all of those have been jokingly, but I have always thought that behind every joke there's some hint of truth
2 - His jokes have always become "closer" to returning. I don't think that's a coincidence and he is getting psychologically closer to the team
3 - Since he retired, he lost a lot of weight... but recently he has gained some back, at least by the pictures i saw of him.
4 (and more importantly) - We have (potentialy) a Goliath of a team. Except for the Lines, we have 2 great talents in EVERY POSITION. It's uncanny. Offensively, Gordon, Edelman and Brown are already too much for pretty much every defense around. If there is HISTORY in the making (and SB is enough history), wouldn't Gronk want to join the Party?
Gronk loves parties...
I don't think he'll certainly come back. But i wouldn't be surprised anymore, for sure