Next season will be a difficult challenge for Alonso in maintaining their performance, because after all the rival teams will strengthen their squad very well, so indeed Leverkusen is also required to do the same by bringing in some new players to be able to compete next season, I personally doubt a little if Leverkusen can repeat their glory next season because indeed tighter competition will occur both in the Champions League as well as domestic leagues.
I believe Leverkusen still has the potential to become Bundesliga champions next season. I put Leverkusen as the first favorite and Munich as the second favorite to win the Bundesliga. But I'm not sure they will be able to win the UCL next season. This season Leverkusen has really impressed in the UEL. They managed to reach the final but unfortunately they lost to Atalanta. Hats off to Alonso who has succeeded in turning a mediocre team like Leverkusen into a very solid squad. Alonso will always be remembered as the coach who came closest to achieving the invincible treble, a prestigious achievement that as far as I know has never been achieved by any coach in Europe, or even in the world.