Bayern already has a good coach in person of Thomas Tuchel and they've got no plans of sacking him yet, however Liverpool still got more contract with Klopp and could however still move for Xabi in a case where Klopp seek to retire but I think the best option for Xabi to move to would be Realmadrid cause they've got a good board and owner that would back him up with funds and help him sign the rightful players to enable him succeed.
I personally believe that Xabi Alonso actually has a great chance to be the Real Madrid coach. he was a Real Madrid player. He had played for Real Madrid for quite a long time if I recall correctly. Be able to do very well as the coach of Real Madrid. I said that because he is already showing incredible results with a team that is nowhere near the power of Real Madrid. So imagine what he will do when he becomes the coach of Real Madrid.
Personally, I don't think that he is going to stay at Bayer Leverkusen. He should push to be the coach of Real Madrid. And if for some reason that somehow doesn't end up happening, I am also pretty sure that there are going to be other clubs who are going to be very happy to get him as their coach.