PSG did this milestone with many young players who potentially improve themselves more and become better players in future seasons. So PSG don't actually have urgent need of buying new players in this summer but perhaps they will try to find and sign. with some young players as part of their long term developments.
While the average squad is quite young, trying to prepare for the future is always a good thing. Especially if the competition in the market gets quite harsher with so many clubs having more money to spend in the future. Not to mention, we know what happened with a team that failed to prepare for regeneration quickly, like City or Liverpool, a few seasons ago. Attracting young or promising players when you have a "UCL winner" is also easier, so it is a good thing if the scout department moves quickly. I think Liverpool has already signed a new young GK in this window, shortly after they signed a new GK and loaned their third-choice GK (which is also not bad, afaik).
Who knows, maybe that will help the competitiveness of the squad and help them clinch another UCL next season.