The only thing that remains to be seen is can he adapt to the times when someone new comes along and reinvents the wheel, so to speak. Guardiola essentially was the peak of the late 00's, to now, possession based Tiki-Taka style football. What made Ferguson so great was every single time there was a new style of play invented that rendered previous stuff obsolete, he always completely adapted quickly. In the late 80's, early 90's, Fergie played with a more defensive mindset as was the approach back then. Flat line of 4 defensive defenders, Midfielders who could all put a shift in, and two strikers to provide most of the goalscoring/attacking threat. In the late 90's, early 00's, he switched to a dynamic midfield of ball carrying, ball playing CM's to be able to quickly switch it to the Wide players. These wide players would carry the majority of the creative threat, one of the forwards would drop deeper and intersect the lines whilst the other led the line. The paradigm completely shifted in the mid to late 00's, where your Beckhams, Giggs, Cameronesi's of the world stopped being as effective. Instead Fergie pivoted to Inside Forwards, using dribbling and ball carrying widemen who could both carry a low ball threat as well as a direct goal threat. United went from a flat 4-4-2 to a more 4-3-3 style over a period of 2 decades.
Guardiola's style since Barca, Bayern and City has always been the same, with some tweaks here and there based on the players he has at his disposal. When, the paradigm completely shifts, it will be interesting to see if he adapts too.
As well as doing it from the bottom up, I guess, but he'll never get that opportunity to. He's not exactly going to join Bolton Wanderers and try to make them PL Contenders is he.
