They have worked so closely together that it would be hard to believe Sir Alex wouldn't go if he won the League and Champions League. But he still has his enthusiasm and might just stay another three years.
Between the bookies, the media and the fans there will be an ongoing circus of trying to guess who his successor will be. Many people still seem to think that Jose Mourinho is favourite now that Pep Guardiola has gone to Bayern Munich.
Sir Bobby Charlton is apparently not in favour of Mourinho and there are suggestions that the choice of successor will come down to either a "big beast" or a younger man with the potential to take United forward for another 25 years.
In the former category, even if Mourinho is ruled out, you cannot count against Guardiola, despite his move to Germany. In many ways it takes the risk out of a United appointment. German football is much more similar to English than Spanish is. If Guardiola thrives at Bayern he could look even more attractive to United.
There are few other English speaking candidates with the CV, credibility and personal makeup to succeed Ferguson.
When he announced his retirement nearly 10 years ago, Ottmar Hitzfeld looked one of the most likely candidates, but he is now too long in the tooth. If the appointment had to be made this summer, then Carlo Ancelotti or Jurgen Klopp would be more likely candidates.
The likelihood of an internal candidate
The last time United made an "internal" appointment was not a success. Wilf McGuinness (father of Academy Coach Paul) was probably Sir Matt Busby's own choice but for whatever reason it didn't work out. Frank O'Farrell succeeded him and that wasn't a success either.
So if there is any likelihood that Sir Alex might favour David Moyes as an external candidate, why not go for someone who has come through the ranks at Manchester United? After all, they will have a much more intimate understanding of the club's workings and its current players.
With Mark Hughes having excluded himself by managing City and failing so dismally at QPR, there are relatively few candidates.
While it is likely that Paul Scholes and Rio Ferdinand might take on coaching roles, the most likely managerial candidates are Ryan Giggs, Gary Neville and Ole Gunnar Solskjaer.
Reading manager Brian McDermott is one of those who thinks Ryan could have a career in management. Gary Neville is doing an excellent job on Roy Hodgson's England coaching staff and has even persuaded non-United supporters of his credentials as a pundit with Sky Sports.
One cannot help assuming, however, that Sir Alex may have personally encouraged Ole-Gunnar Solskjaer in his ambitions as a manager.
So why might he be the most credible candidate with Guardiola gone to Bayern Munich?
Ole-Gunnar Solskjaer's credentials
Sir Alex has always been impressed with Solskjaer's reading of the game, even as he sat on the substitutes bench. He is in no doubt that the Norwegian can succeed as a manager.
Indeed Ferguson endorsed Solskjaer's appointment as Reserve team coach before he left to manage Molde.
And he was the first to congratulate Ole when his team won the Norwegian championship and qualified for the Champions League for the first time in their history. Their subsequent lack of success is irrelevant given that some at Old Trafford believe that Champions League experience is one of the prerequisites to succeed Sir Alex.
While Ferguson counselled against Solskjaer coming straight back into English management with Portsmouth (that was a near miss!), the above quotes make clear that he expects the Norwegian back some time in the future.
Depending on the timing of his own retirement, would Sir Alex therefore endorse Ole as his successor?
Certainly the Manchester Evening News (probably as close to United as any national newspaper is) seems to think that Solskjaer has real credentials.
The bookmakers aren't entirely convinced yet. While they do at least have him as fourth favourite, his odds vary from 6/1 out to 20/1. Mind you, David Moyes is outright favourite; Guardiola and Mourinho remain joint second favourites.
The thing is, if the select group who will recommend the appointment to the Glazers were to agree on Solskjaer as the "compromise candidate" between the competing arguments of the other three, they will surely want to see a United bred management team.
This must surely mean that there would be roles for Giggs (as attack coach) and Neville (as defensive coach) alongside the Norwegian.
You can be sure that there would be no dissent between those two or among the players about having Ole-Gunnar Solskjaer as manager. As a United legend he would also quickly win support outside the club as well.
For the time being, however, there is no way of predicting who will succeed Sir Alex. While he is apparently in control of his own departure, he will only be one voice when it comes to deciding his successor.
You can be sure that the appointment will be watched as eagerly as the anointing of a new Pope and possibly by almost as many people worldwide.
While it is potentially a "poison chalice," of an appointment, it will probably come down to a unanimous decision between Sir Alex, David Gill (who is remaining on the Board), new Chief Executive Ed Woodward (on behalf of the Glazers) and Sir Bobby Charlton.
Senior representatives of the players may also be privately canvassed on their views because of the huge esteem in which Sir Alex is held.
While Ferguson might favour Moyes, the "money men" might want a "heavy hitter" but it seems likely (from the earlier quotes) that Sir Bobby would be against Mourinho. If Guardiola has failed in Germany, or is not available, Solskjaer might just be the one candidate everyone could agree on.
It is likely that some will see David Moyes as having insufficient European experience, despite Sir Alex's possible favour.
But then we still don't actually know when Sir Alex will retire. If Gill's move upstairs is a precursor to this, some might think it was a little early for Giggs or Solskjaer. In that case, a compromise might be seen as the best way forward, supported by one or more of the "internals" in the coaching team.
If that were the case, you could not rule out Mourinho. The one thing against him is that he has never stayed longer than three years. But he does have this irritating habit of being a winner. If he would be prepared to accommodate Solskjaer and/or Giggs in his coaching setup this might be the dream ticket, with the younger man to step up in due course.
Carlo Ancelotti would also be an excellent choice for an interregnum period.
The other possibility is of course that Sir Alex is asked to take on Solskjaer as his number two with an expectation of succession at the Boss's time of choosing.
That would seem to be the ideal solution. It gets over the alarming consequences of what happened 10 years ago, or a sudden departure by Sir Alex; it allows for a seamless transition; and it would also enshrine possibly the best "internal" candidate to ever emerge at Manchester United, Ole-Gunnar Solskjaer.