Florian Wirtz seems like secured for Leverkusen for at least next season. Normally it wouldn't be much possible but Xabi Alonso effect changed everything for Leverkusen. They started to believe in themselves to achieve any title available. 
Therefore I also think Wirtz doesn't need to leave already now. He is only 21 years old as well so there is no need to rush while doing wonders with his team.
But in the summer of 2025, it seems like it will be very difficult to keep him. Real Madrid and Barcelona are already monitoring him according to rumours. As long as Leverkusen doesn't win the Champions League title I don't think he would stay.
Therefore I also think Wirtz doesn't need to leave already now. He is only 21 years old as well so there is no need to rush while doing wonders with his team.But in the summer of 2025, it seems like it will be very difficult to keep him. Real Madrid and Barcelona are already monitoring him according to rumours. As long as Leverkusen doesn't win the Champions League title I don't think he would stay.
I know rumours already all rounder linking the youngin to Real Madrid and Barcelona but t's best if he stays put one more season with Bayern Leverkusen to see what they can achieve in the Champions League Competition and how far they can also go. Yeah, I love the fact that they won't be having too much players leaving the club as it will help strengthen the squad by adding rather than letting go or selling.
There's no need to rush but whenever Real Madrid comes knocking, you don't have to think about it twice. Take a good look at the Real Madrid squad Luka Modric would be gone next season at the end of next season so they'll be needing this guy to support in the middle of the park.
My guess is that Xabi Alonso would also be coach for Real Madrid by the year 2025 or 2026. We will see, this is just a prediction.
I have said earlier about joining Real Madrid, maybe he should move to a side between them where he can have enough game time. Winning the Champions League Competition is no excuse, if Real Madrid comes for me while playing for my local club, Parking up is the next thing in my skull.