A change of coach can give rise to two options, either the club's performance will be better or it will experience a setback from before. If you look at the coaches recruited by Bayern Munich and Dortmund, the potential for Leverkusen to retain the Bundesliga trophy is a little more open. The reason is because both coaches are not experienced enough to handle big teams like the two of them, while Xabi Alonso has very strong and solid strengths.
I don't think Leverkusen will be able to achieve an unbeaten record again next season and that is something that is difficult to maintain. But in terms of the title or finishing in the top three, Leverkusen still has a chance as long as Xabi Alonso can make his team play more consistently like the previous season. Next season Leverkusen will also play in the Champions League so they will have a busy schedule with much tighter preparations to take part in this competition.
That makes sense, Xabi Alonso will of course have big ambitions to improve the performance of the Leverkusen team next season, especially with the achievements they have achieved this season making it very possible for them to continue.
Meanwhile, Bayern Munich, with its new inexperienced coach, of course needs time to adapt and it is slightly beneficial for Leverkusen to be able to defend the title, but Bayern Munich still cannot be underestimated.
Because Xabi Alonso will be playing in the Champions League, of course he has to be able to build this team to be much stronger than last season, I think that's quite possible and regarding their unbeaten record they might maintain it, but that's in the Bundesliga, not in the Champions League.