I agree with you that Borussia Dortmund may not be able to repeat there performance they had on this season to this upcoming season because just like you said they defeated PSG and Atletico Madrid but with all the amendments and strategies those clubs has put in place there is no way Borussia Dortmund will beat them and besides it was even fortunate for them to have win them because normally PSG is more in a good shape than them so wining then was actually a narrow escape, however one of the things I even noticed about Borussia Dortmund performance is that there performance is always seasonal because at a moment they will be very inform and the next season they will start performing poorly.
Although the quality possessed by Dortmund is not equal to that possessed by Madrid, but I think their performance last season was very impressive, especially in the Champions League, since the round of 16 began, Dortmund is one of the most underrated teams due to their poor performance in the domestic league, but slowly we all begin to change our view along with Dortmund ability to destroy Atletico Madrid and also PSG to reach the final Champions League, Champions League this season in my opinion gives us a surprise which should indeed change our view to no longer to underrated of a team playing in the Champions League.
Currently Dortmund who has indeed replaced the coach, of course still has a big ambition to repeat their performance and achievements in the Champions League next season, although Dortmund is a team that has financial limitations but I think they will still be able to compete by relying on the talenteds they have had so far, next season I think Dortmund will be a competitor in the Champions League especially since they have now brought in a striker who performed quite great last season with Stuttgart.