Everything can happen, especially in this stage of the season and the final stage of the game. Real Madrid needs to be careful with Dortmund because they are not a team to underestimate; they can make a surprise move. Although Real Madrid are stronger and they are doing better than Dortmund in all aspects, in this stage of the season we should not underestimate any team opponent. Since this is the final, you can see that Dortmund will do everything possible to see them win the title, but I think it will be very hard for them to achieve that because of Real Madrid's consistency, so let's see how they will do and who will win the league title, even though I consider Real Madrid to win.
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.
Considering real Madrid to be a winner might definitely happen because that's what everyone are anticipating due to how their performance prove through out from the started of this season and come to an end of the season, in my own view they will find this final very easy with out any challenges.