Man City are probably the best club in Europe right now, but don't forget how they only managed to push Arsenal out of first place at the end of last season... So there are strong clubs in the EPL now too... I think that next season Man City will not be as easy as last season and I don't rule out the possibility that they won't be able to win again...
If the top clubs in the EPL still maintain their old players and don't add or overhaul their team squad it might be a bit difficult to compete with Manchester City, so far Manchester City already has several quality players even though they have several players who have left but they are adding players new additions to complement the departed players so the team will remain solid.
Guardiola will defend the Manchester City title this season, of course, by overhauling a few of their squad team players so they can win the EPL again this season and what is most expected is to get a treble winner for the second time, if you look at some of the players in their squad it was enough for Guardiola to bring Manchester city back to being champions this season.
Premier League teams always improve much better and this competition is very competitive, Manchester United, Chelsea, Liverpool and Arsenal certainly target to become champions regardless if Manchester City is much stronger between them but the competition to become champions will certainly remain fierce.
It cannot be denied that Manchester City's current strength is quite strong, but I think for them to win the Premier League title will not be easy.