As for Leverkusen, once they change their coach, I believe their performance will remain the same with their current squad. However, if they bring in more quality players, it could greatly help them. Still, I think the new coach taking over from Xabi Alonso may have the chance to give Bayern Munich a tough time.Since Bayern has won the Bundesliga now, they may aim to sign more quality players to strengthen their squad. If Bayern Munich succeeds in doing so, I don't think any team may challenge them effectively.
Munich with the same coach and with a little change in the team, might perform better next season. But Leverkusen with some changed players and a new coach, we still can't say how good they will be next season. They can be good from the start, but there is also a possibility that they will need time at the beginning of the season to adjust.
I just hope Munich doesn't lose to the rival teams. Dortmund is already in need, and if Leverkusen is not good enough next season, Munich will dominate.