Dortmund achieved nothing and there is no reason for them to be happy after this year.
In fact, they lose what they could get easily and maybe even years after that they won't have this chance to have a close race with Bayern Munich and have Bayern Munich in this situation.
I also think that the outcome of this season was very tragic for Borussia Dortmund. The sad reality in the Bundesliga is, that other teams only have a chance to become Bundesliga champion if Bayern Munich is playing a very very bad season for their standards because otherwise they are just to strong. This season that was the case and still Borussia Dortmund somehow managed to screw it all up in the very last match. I think they won't get another such big chance again so quickly.