5 years matches what he did at Barca and I do not equate that to long-term. To that point, he is closer to his departure than his arrival - irrespective of the renewal. Yes he honors contracts but he also will have included a clause to permit him the freedom to walk away for Barca or for any other reason Guardiola choose. Let's not forget, apart from the ownership the rest of the management team are the same ones he had at Barca
Sancho is not an academy product of City, no more than a mercenary who simply spent a short spell there - same for Iheanacho, they flourished ultimately away from City and also why I pointed out this is not necessarily a poor formula since it has worked well for Chelsea too
It's profitable now but even at it's outset with the oil money, their aim was to build Barca-lite. If Pep leaves, you lose a considerable part of that Barca formula you count on. City are not supported at the same level in terms of fan as say the other top clubs in England. City can be discussed as a big club currently but that can quickly change due to personnel - the long standing joke has been how empty their stadium can be or traveling support. Before the sheikhs arrived, they were relegated for a period of time. They will always be quite liquid in terms of resources but how will they maintain a working model long-term without key custodians to ensure continuity of success from a coach or management team? I also think we do not know the long-term investment strategy of sheikhs
I also do not agree that Chelsea differ greatly from City in terms of ownership, both are bankrolling the club - one just has much better PR to give the illusion of financial good health. Even UEFA tried repeatedly to punish them which, at the very least, underscores the creative accounting that goes on at this level
United will, long-term, always dwarf City. Only a City fan would dispute that in all honesty. United for all the reasons to hate them, despite having no real playing philosophy will always generate revenue, have huge fan support and players who will want to play for them. Today, sure, a bonafide star would choose City. Tomorrow, once Pep is gone, then that decision becomes a bit more pragmatic (Money + club stability + sporting outlook)
Right now that harmony is ideal but there is nothing to suggest this will persist once the key architects leave