Possible everything can happen but not mean that Dortmund can find coming final against real Madrid easily to win it will be very difficult for them to overcome real Madrid. Because they cannot compare performance of real to Dortmund, everyone knows how their so good and very strong this season so predict that Dortmund can surprise people's by defeated real Madrid I think is very early to predict that, But shall let wait and see what can actually happen on Saturday between the real Madrid and Dortmund.
Dortmund can beat Real Madrid but they must have a very wise and proper approach in tactics for the final since its beginning. Real Madrid with their experience and quality, can score goals any time and if Dortmund show their defensive weakness, make mistakes too early, they will have to pay very high cost.
If Dortmund start the match defensively, defend well, they will have bigger chance with time when Real Madrid players will feel like no dangerous counter attacks from Dortmund, lose their patience and try to lift their squad higher and higher to find a goal. It will be time for Dortmund to use counter attacks to invade Real Madrid midfield and defensive areas, and get a winning goal.
I consider Real Madrid will be the champion, not Dortmund but as analyzed, I see chance for Dortmund.