@Bob Barnes may have some insight on how many attended the Synergy Camp and could be helpful, IF you can nail him down.
I think the interest for something like this is usually 8-10 out of the 60 or so attendees, mostly advanced skiers. There may be some interest for some beginners or timid skiers but that number is usually moderate at this type of GTG.
I was planning to take a private lesson, whether before the Gathering or during. But if some kind of Epic group lessons are setup during the Gathering, I'd be happy to attend that - though I'm a middling intermediate, so skill level may be an issue.