In local media, Leverkusen have not been willing to release Xabi Alonso to leave. I don't really understand this reason is because of the team or the money. But if you look at Leverkusen's stats with Xabi then he really deserves to be retained. But maybe this is also a tactic to increase the selling price. Real Madrid have to start thinking, because Anceloti will definitely go to Brazil. There are several names who may be on a par with Alonso and they are former Madrid players, such as Raul Gonzalez or Alvaro Arbeloa whereas Zidane is unlikely to ever coach the club.
As far as I remember, Xabi has a contract duration until June 2026 with Laverkusen, of course the management is not too worried about the next three seasons. However, Xabi can also end his contract early and leave Laverkusen if he receives a high salary offer from another club. I think currently Xabi has the ambition to win the Bundesliga Trophy with Laverkusen, if he can win it will be proof of the quality he has.
I think Xabi is still better than Raul and Arbeloa, Madrid seems to be prioritizing Xabi. It is reported that De Zerbi, the Brighton coach, is also currently on Madrid target list, this could be the second option if Xabi fails to be brought in from Laverkusen.