The answer is classified <g>
/Admin
I almost expected an answer like this...
Anyway, I hope it will be STS-39.
I think this would be a good choice, because there is a lot of official information available, as it was unclassified. It also seems to have been a quite complex and interesting mission: Five satellites/spacecraft were deployed, one of them was retrieved later, some RMS operations were involved and some interesting maneuvers were executed in orbit, including one that is affectionally known as the "Malarkey Milkshake".
Well, whatever the new mission will be, I hope it is going to be ready soon, as "the crew" (me) is already impatiently waiting for it.