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.
A lot of clubs are keeping a close eye on him since last season and this summer he there should couple of teams competing for his signature but he will be staying an extra year because of his commitment for Xabi Alonso and also winning the Bundesliga title changed it all. Of course one day most of these star players will leave Leverkusen but for now they all seem to be committed to play an extra more season for Alonso. Definitely if Alonso should leave next season Leverkusen will lose a lot of players as well and Wirtz would be top target for top clubs. 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.Quote
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.
Not just Barcelona and Real Madrid even top teams from England are keeping a close eyes on him and i believe Bayern Munich will also join the race as well. He is a German player and he may consider joining Bayern Munich over other European teams.