It certainly changed the mindset of a lot of them, more so those who didn't see the shite pre 92 with sub 20,000 crowds. They initially had 4 good seasons in the Premier League but then 4 lower half finish seasons until 2001/02. They had another 4 out of 5 top 10 seasons but that's it as the rest of the time they've been as they were, lower table.
Only the wiser amongst them will know they aren't the 'consistent' top half club some other fans try to make out. They way they were going with Hall wasn't a sustainable way of running a club as Leeds and Blackburn found out and Newcastle nearly did until Ashley walked in (though didn't he not fully check the books?).
Fuck know where they'd be if Hall hadn't come in and brought Keegan with him. The Premier League was developing and Hall came in at the right time to jump on the big money bandwagon. The money in the game was growing quicker than the wages/prices for the players and some of it was spent wastefully trying to buy success. Teams can't spend willy nilly now as they'd eventually crash and burn. Ashley isn't investing as much as the Mags would like but is the club losing money season after season?
I think someone will come in a invest a bit of money into NUFC but they will have to think about financial sustainability also. That's why I think even if PIF came in the Mags would be in for a shock. I don't think they'd be spending millions on top players on big wages but rather put just enough in so they can flip them for £500+ million at some point. Or someone comes in and spends big money banking on future revenue which is banking on some success. However, they fail and the Mags end up in a shit load of debt