Lol, he would never leave Bayer Leverkusen during a season. I don't believe that rumor even exists, but if it does I would immediately say it's a bad joke.
Alonso is going to give his best for the team now and I think that it could be possible Real Madrid is trying to get him for the next season. But Alonso has all the time he wants, he is still very young as a coach and if he now builds a great team in the Bundesliga, maybe he wants to stay with them for another season and keep the option to go to Real Madrid one day in the back of his head. There is really no need for him to rush anything.
Any coach would be very happy to coach Real Madrid if an offer came to them, including Xabi Alonso. But I agree with you on this matter, it is very likely that Xabi will only be ready after achieving success with Laverkusen first. Considering that this achievement will be proof of his quality when one day he coaches Madrid, we know that controlling Madrid dressing room is not an easy thing to do.
Maybe Madrid management has already pocketed several names to replace Ancelotti in the future, including Xabi. However, I think Zidane also has the potential to return, but there is no certainty yet, we can only wait and see the contract renewal for young Madrid players first.
I also believe the same thing, but this season is still very long so there will be a lot of rumors about who will replace Ancelotti if he really wants to leave. Xabi Alonso doesn't seem ready to lead Real Madrid next season, but he could try if he gets an offer.
Real Madrid seems to prefer getting an experienced replacement compared to a new coach who doesn't have much experience. Several names are of course already on their side to consider, but I believe Alonso might be a good option, especially because he already understands a lot about Real Madrid during his time as a player. There will be no surprise if Alonso ends up coaching Real Madrid next season, but I would really be surprised if Zidane reunites with the same team after rejecting several offers from other teams, including those in the Premier League.