I would be very surprised if Bayern Munich does not retain the league title this season because all the teams that are currently Bayern Munich's opponents in the German league have not been performing very well recently, so it will be relatively easy for Bayern Munich to retain the German league title this season. Bayern Munich's performance can be doubted in some aspects because this season Bayern Munich's important players have left for other clubs, on the contrary, Bayern Munich has not recruited any good quality players in their place. If multiple injuries occur in the current Bayern Munich team after the season starts, it may have a bad effect on their good performance, which will show that they are not able to perform as well as they are supposed to.
Hopefully, such an accident will not happen to Bayern Munich and they will finish the German league with 100% success next season.
Comparing Bayern Munich's strength with other teams', the difference is quite significant. Bayern Munich is dominated by high-quality, big-name players, while other teams have relatively sold their star players in the transfer market. Bayern Munich certainly won't waste any opportunity in every match, chasing points to defend their title this season.
Other teams' performances aren't particularly bad, but to compete with Bayern Munich, they will certainly need to perform at their best, perhaps making it difficult for them this season. Xabi Alonso's departure from Leverkusen certainly means Leverkusen will have to start a new era with a new coach. Surprises are always a possibility in football, but in the Bundesliga, they are rare, as Bayern Munich dominates everything compared to their rivals.