I wouldn't be too upset if he went Bayern. I think he is slightly overrated as a player. We need to try stay clear of these signings where a player has so many options.
A few bad results / performances and you will hear should he have gone to United, and he will come in and think he is the best defender there is because of the hype on him.
Look at the players that have done for us recently, they all have hunger to play for Manutd for a long time, not be a stepping stone for Madrid or Barca.
Disclaimer: I do not know his personality, I am not saying he is a bad apple.