Its going to cost them fortune to get Xabi Alonso and as of now, I bet he is a Top tier 1 coach that any team would be willing to hire. Imagine winning (almost) Bundesliga with Bayer Leverkusen against the all season dominating team like Bayern Munich then after that he pick a team like Liverpool that has alot to do for their next season after Klopp leave
He will has better chance on sticking with a top club in Bundesliga like Bayern Munich rather than taking chances for now. He still has plenty of years ahead of him if he wanted to get some challenges though
I don't know what's the plan of Xabi Alonso for the next season. We have some rumors about him, Liverpool and Bayern Munich are 2 teams to compete for signing him. But it is no clear which offer Xabi will consider.