We can pretty safely predict that won't happen because Henderson isn't good enough to warrant a 50m outlay to bring him back as our first choice to be Manchester United's next #1. If/when the time comes to replace De Gea, there will be other better options out there we can target.
Henderson got his shot here a couple of seasons ago because he was already a United player and De Gea was poor. Had Henderson not been a United player, we certainly wouldn't have been looking to install him as United #1 after one good season at Sheffield United. Once we sell him he loses the key aspect of his appeal, which was that he was already a Manchester United player.