Surely it would place a massive asterisk on all the trophies won during his time at Man City? In future discussions on the greatest manager would this be a talking point which stains our perception on him? Or will he still be lauded as the greatest by some despite the wider context?
Imo yes it will put a bit of a stain on his time with the club, but it wont change the fact that hes a great manager. Hes proven himself time and time again to be one of the best managers in the world, and done it with multiple teams. Hes also been one of the most influential figures in modern football. Seems like tons of teams look to his lineups and tactics for ideas of what to do and how to move their team into the future.
So yeah man city being found guilty of record breaking amounts of cheating financially will probably make us think less of the team as a wholes success, and that includes his, but it will not remove the great work hes done as a career.