To repeat the unbeaten record in the Bundesliga is indeed difficult, but it is not impossible for Leverkusen to happen again under Alonso's guidance next season. However, remembering that this is something that is not easy for Leverkusen to repeat, of course there is a possibility that Leverkusen could lose in the Bundesliga next season even though Leverkusen is still the favorite to win the Bundesliga.
Of course, it is not impossible because Leverkusen still has almost the same squad and the same coach. We can assume that Leverkusen is still as strong as the previous season. However, other teams in Bundesliga can be stronger, they also already learn many things to beat Leverkusen in the next season. So, the chance to get losses will be higher in the next season. The teams in Bundesliga are familiar enough with Leverkusen game style. Even, they already learned how Atalanta could destroy Leverkusen. It is an important match to be analyzed by all the teams in Bundesliga.
Anyway, Bayern Munich already changed their coach with a new one. Vincent Kompany is the coach of Bayern Munich now, he may bring a new spirit to improve Bayern Munich performance. Although Kompany has lack experience in managing big teams, who knows if he can also be successful as Xabi Alonso. Nowadays, a new coach can give a big surprise. It is not only in Bundesliga but it also happens in other leagues such as in Serie A and EPL. To be honest, I really expect that Kompany can improve Bayern Munich. So the race for the title of Bundesliga will be interesting again for the next season.