I can't say that PSG will be able to win the Champions League next season if they maintain their performance because other clubs might have increased the strength of their teams with new signings. PSG haven't signed any player yet, because they feel it's not important which might later become a problem for them next season. This was how Leverkusen thought that they are the best and don't need any additional players when the won Bundesliga title.
The Bundesliga title and the Champions League title are like two very different class titles so that I personally will never equate the caste and conditions of the two titles. In addition, Leverkusen won the Bundesliga title before PSG won the Champions League title, so if Leverkusen ever thought like that when PSG still had not won the Champions League at that time (2023-2024), it was very strange in my opinion. Because a team that has succeeded in becoming a champion in a prestigious event like the Champions League should be more enthusiastic in looking for new players in the transfer market even though not in large numbers.