AH! Ok, so back in May Duran Duran played here in Chicago, and Billy came on stage to play a song with them.
After the show, we were at the same bar as most of Duran Duran, so I went up to Simon le Bon and thanked him for having Billy play with them. He got very excited and went on and on about how much he loved Billy and Smashing Pumpkins. They had played a festival in Australia together a month previous, and both Simon and John Taylor wrote gushing things about Billy and Smashing Pumpkins in their blogs on the Duran Duran site.
At some point Simon got very excited and asked me "What would you think...if we played a WHOLE SHOW...with Smashing Pumpkins?" and I looked at him like

and told him that would be The Most Amazing Thing Ever. I asked him if he thought it was possible and he said "YEAH!". And I told him to make sure they played Chicago and he said "YEAH!"
Duran Duran is my favorite band and Pumpkins are a very close second, so there aren't any words I can think of for how excited I'd be if this really came true.