There's no doubt that Leverkusen performed well last season. After a long time, the Bayern Munich team lost their dominance in the Bundesliga. However, I don't think Leverkusen will dominate the Bundesliga this season as they played well last season. Serie A side Napoli were champions in the 22-23 season, but performed very poorly in the 23-24 season. So I would say Xabi Alonso has to be very careful this season.
Bayer Leverkusen can't be that bad next season but I believe they can never be seen as the Bayer Leverkusen of 3-4 seasons back, what I mean is that they are one of the big boys in the German league and their games will attract attention more because of how they carry the game and how they performed by dominating one of the strongest of all time Bayern Munich.
Imagine Alonso repeating the same thing by making it difficult for Bayern Munich, I think that would be the end because it only shows that Munich have lost that strength of getting back that glory and Leverkusen is a worthy champions but I can't say it will because even Dortmund are also getting ready to over shine Bayern Munich and the current Champions Bayer Leverkusen.
In Serie A I think is something that always happens when a team win the title they become useless the next season with a very poor performance and you'd be tempted to ask if this was the team that won the league or is there something wrong somewhere? I think is only when Juventus was in their prime that they won their league title severally without doing bad the next season but for Bundesliga I think it will be a different show, Bayer Leverkusen can still retain the title, even if they don't I believe they won't play very bad like Napoli did in the Serie A.
I will be happy if the Leverkusen team continues this great performance next season. Because for 12-13 long years we always saw the dominance of Bayern Munich in the Bundesliga. And before the start of the season we knew that Bayern Munich would be the champions of the Bundesliga. And all the other teams were only playing for Champions League qualification. But Leverkusen's impressive performances last season broke Bayern Munich's dominance in the Bundesliga. After a long time we got to see a new champion team in the Bundesliga.
Xabi Alonso has played the most important role behind this overall change of Leverkusen. Hopefully the Leverkusen team will perform better with the help of Alonso in the next season as well. If the team can perform consistently well in Leverkusen, it will be very difficult for Bayern Munich to win the title next season. And the Bundesliga will also become very competitive.