Assuming it's playable there (my understanding is that it hasn't been officially confirmed, though I would be pleased to be corrected), we should be certain about wavedashing, know the special moves for any character they let you play, and figure out a host of other things.
The only problem is that the Smashboards server probably will drop to less than a crawl when people start reading about and commenting on the threads started by those who make it to the event.
We'll probably end up with a final major thread about wavedashing that either joyously confirms it or mourns at its departure (since most of those capable of reliably testing its presence want it in), that will begin with a vicious debate about whether that was a good choice, and where a few scrubs make a final attempt to convince us that competitive players don't have fun and a few competitive players tell them that they suck, and then yes, the debate about its presence will die.
EDIT: Last I read about it being playable, it was still rumor. It appears that it really is official. Now, if only it wasn't 600+ miles away...