Dortmund is a team that will perform well in the upcoming season. But they will bring some unexpected results. my prediction is that they are going to win against some very big opponents which was not expected from them but at the same time they might lose or against some relatively weak opponents.
Yeah for sure Borussia Dortmund are going to have some big wins but they will not be able win the Bundesliga trophy next season, don't get me wrong I no that they have tried a lot on this season but there performance is still not good enough to win the Bundesliga considering their rivals, however even if we should evaluate there performance this season you will see that they weren't doing very well at the beginning but it was on the middle of the season they picked form which even helped them to qualify for the champions League next season, so perhaps if not for that pick up performance they had they wouldn't have qualified for the champions League.
For now the only thing I can say about Borussia Dortmund is that they can only qualified for the fifth or the fourth position on the Bundesliga but in terms of second position it will likely be very difficult because the first and second position will certainly be occupied by either Bayern Munich or Bayern Leverkusen because for now they both have the highest performance on the Bundesliga. But however like you said in terms of Borussia Dortmund wining some good matches they will certainly do because in as much as they may not win the league doesn't mean that they are bad in performance.
Next season I bet that they are going to be third at worst case. Leverkusen and Bayern are still looking strong, but just because Dortmund had one bad season doesn't mean that they are going to stay there. They sold so many players and made so much money because of this, they just feel like they are going to do a lot better and that is going to eb the decision maker.
I think we are going to see the situation changing, we just need them to do a lot better and for that to mean something we should consider how they can improve the squad. Dortmund winning europa wouldn't be that impossible neither too, just being there means that they are going to be the best team or one of the best. All in all I think they are a fine team.