All of this is still just speculation, there has been no official announcement as to where Xabi Alonso will continue his career, whether he will stay at Leverkusen, maybe move to Bayern Munich or Liverpool. Staying at Leverkusen would be better for him, that's my view, because he would have an easier time managing a squad he built with his own hands.
Xabi Alonso's success this season with Leverkusen has received a positive response from other clubs to sign him, he must make a decision for his own good in the future. The decision of where to continue his career is in his hands, I hope he doesn't make a hasty decision that will result in him being disrespected like what happened to Tuchel and Jose Mourinho due to losing too many points in the domestic league.
Speculation about Alonso continues to circulate at the moment and will even peak when it is approaching the end of the season later, so far Leverkusen through his representatives have stated that they will try to keep Alonso in the team next season, and this indicates if there is indeed a desire from Alonso to leave for another team even though he has not confirmed it to the media, I personally am no different than you expecting Alonso to stay at Leverkusen and continue to create records for Leverkusen next season, especially when will they play in the Champions League.
But indeed we do not know where next Alonso will go, but I think Bayern Munich will be a strong candidate to be the next club that Alonso will coach, and if indeed next season Alonso leaves Leverkusen, I am quite sure if Leverkusen will fall back in the league as before, it is not impossible if Alonso's mainstay players in Leverkusen will follow him to move to Munich or other clubs in Europe, With all the achievements Alonso has been able to achieve at Leverkusen, it will be difficult for the leverkusen to keep him because indeed the lucrative offers of elite teams such as Munich and Liverpool will only come once in a lifetime.