PSG surprises everyone in the just concluded UEFA Champions League competition, and they can compete in the next UEFA Champions League competition that will start in a few months from now, but I doubt if PSG can make it to the final because the UEFA Champions League is a tough and difficult competition, and a lot of clubs will rise against PSG when the competition starts.
The champions league is so difficult that sometimes even the defending champion can be eliminated at the league stage of the competition. But am optimistic that wouldn't be the fate of PSG by next season but them reaching the finals of the league again at a row is just more difficult as predicting them to win it again next season. They'll have to do the extraordinary of why they did last season to even get to find themselves again past the semi finals level.
Anyone that feels PSG can defend the title next season is not use to watching Champions League. If not they will understand that all clubs in this competitions are champions and you shouldn't underestimate any of them. PSG was underestimated previous seasons but look at how the wonderfully won the title this season. They can't win it again next season. This is why the league is unpredictable and interesting.