It would be really crazy if it happened but unfortunately Dortmund lost in the finale last night. 
Still it was a nice try though. Dortmund were fighting for their own success of course but they would help Frankfurt at the same time. 
Anyways, this is a successful season for Dortmund technically. I repeat, I don't expect Terzic to get sacked. It would be crazy to sack a manager who has carried this team to the Champions League finale. They have got a ticket for the Champions League next season at the same time. As long as he doesn't want to leave by his own decision I would expect a contract extension as well. His current contract is expiring next summer for now.
You are right, there is no reason to fire him, he led Dortmund to the Champions League final, this is a great achievement for such a team. But I wouldn't be surprised if he gets some good offers from other teams. Terzic is young and participation in the final gave him invaluable experience, he was one step away from receiving the most desired trophy for every coach, I think that he will try to repeat his success, and perhaps he can achieve this with a stronger team than Dortmund, I think he will have such an opportunity. Still it was a nice try though. Dortmund were fighting for their own success of course but they would help Frankfurt at the same time. Anyways, this is a successful season for Dortmund technically. I repeat, I don't expect Terzic to get sacked. It would be crazy to sack a manager who has carried this team to the Champions League finale. They have got a ticket for the Champions League next season at the same time. As long as he doesn't want to leave by his own decision I would expect a contract extension as well. His current contract is expiring next summer for now.