I would expect that if BroadwayCon attendees wanted to attend, they would aim before or after the convention simply because the time commitment would cut into con programming. Unless they are attending just one day or going for one specific event. That being said, I'm not really sure how many people attend the con in total, but I would assume that it isn't EVERYONE'S cup of tea anyway and that the number of tourist drastically decreasing otherwise would even things out.
I concur that you should definitely keep an eye on tickets for a little longer.
So, that was the Drowsy Chaperone. Oh, I love it so much. I know it's not a perfect show...but it does what a musical is supposed to do. It takes you to another world, and it gives you a little tune to carry with you in your head for when you're feeling blue. Ya know?