Unless Beast want to elaborate on his inside info, we can still go on hypothesizing..
My turn:
tree most possible cases for mou's future:
1) He stays with madrid 3 more seasons and he then coaches UTD, as SAF is retired. (i dont think this will happen in the end...)
2) He stays 0 or 1 more season in madrid and then closes the gap of 2 or 3 seasons untill the time UTD need the successor.. Possible destinations in between are leagues he have not conquered yet (Bundesliga? a piece of cake for him. or Ligue A?) or EPl but for an inferior team (Spurs fit the image well)
3) He offloads himself immediately to England, for a top club either Arsenal, Chelsea or City - less likely if Macini wins it this season - and at the same time ruins any possibilities of him becoming what he is longing for: the successor or SAF.
It is really a matter of priorities. Is his priority to coach United for at least 5 + years? Then number 2 is his option.
If he cannot wait however, then number 3 will soon happen, but we will never see him in old trafford in that case..