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.
I'm very sure Real Madrid Is very experienced enough in the champions league as this isn't their first champions league finals so they know how well to handle situations as this and are very much aware of the possibilities around unforseen circumstances that may arise in course of the champions league final game hence they will know how well to handle such if any may arise as there may possibly be preparations for such a aswell just should Incase any of such comes up.
Dortmund too may not be ignorant of the chances they have got around this game and will definitely want to see how well they can utilize any of the possible chances that eventually gets to come their way, the game has been kept far enough for both teams to get adequate and probably the best preparations they can get for the fixture as they both know what it entails and what it's worth aswell, which is the reason they would really want to get to doing all of such preparations to get the team to be in their best of form and strength to be able to win because there's definitely going to be a winner not minding how well both team play .
Real Madrid still remains the favourite of the vast majority and it's obvious in the fact that their performance this season and their records which has accumulated to been their experience in the champions league is such that have earned them all the support they are getting that is making them appear as the favourite even if we all know that Dortmund isn't a weak team but it appears to most persons they have a slimmer chance of winning than Madrid.