The club that can still be a serious threat to Bayern Munich is Bayer Leverkusen because the club will still be coached by the same coach so the strategy will probably not be much different from last season, although some may be changed to make it less easy for all opponents to read. I also think that Vincent Company has the ability to train Bayern Munich's players next season, but this will also be quite difficult for Vincent Company because considering that Bayer Leverkusen can still be better than last season in the Bundesliga next season.
By the way, it is quite possible that Bayer's success could affect the mood of Bayern, if Alonso can again repeat his unbeaten streak, then Bayern will not easily perceive that they have lost their dominance in the Bundesliga. And for Kompany, winning the Bundesliga should be the easiest way to get a trophy, because letting Bayer do it twice in a row would be a bad sign, and I doubt that Kompany can achieve anything in the Champions League.