I too think (hope!) Romeo and Juliet or Tristan and Isolde. It would be terrible to have these two never have a R&J program. Although, it does seem kind of obvious and predictable. Marina has said that she's known for a while what they would use, so that could be why they haven't already done it. I could also see her giving them some beautiful but relatively unknown piece and just letting them tell their own story, without characters. That would probably be the best set-up for another OGM. No one does that like the two of them!
In other news, since they declined to go to WTT (as did D/W), we've seen our last performance of Carmen. I'm going to miss it!