I don't sure PSG will get downtrend performance for next season after leaving by Kylian Mbappe, its difficult decision accepted by PSG after Mbappe not extend his contract but Luis Henrique will make PSG keep dominance in Ligue 1 and reach higher level round in Champion League next season. Have break out almost two months before next season begin I think PSG start to sign top players for replacing Mbappe position although they can put Goncalo Ramos as central forward for Mbappe position.
All top teams when leaving by their favorite players can recovery well and the empty position replacing well by other player, I remember with Real Madrid after leaving by Cristiano Ronaldo replace well with consistent perform of Karim Benzema. Not close possibility with PSG performance for next season better than their performance in this season although leaving by Kylian Mbappe.
I do not think that "higher round in ucl" seems possible considering they were already at semi finals, and Dortmund manage to beat them, so higher would mean finals, and I do not see them getting to finals without Mbappe, that seems like an unlikely situation.
However, I do agree with the situation that they are going to dominate ligue one again, that seems like the most likely result. That doesn't mean that we are going to see things that would be all that complicated, we are talking about just stuff that would be normal for a team that rich to end up getting a win in the league that doesn't have even quarter the amount of money they have. It would be a bigger news if they lost, so it is going to be expected for them to win that.