Besides announcements, including the big 4.0.0 mega-expansion, players would get to hang out and talk to devs, play demos, buy merchandise, party, and revel in swag. On top of that, there would be finals to various tournaments. GGG also wants to run competitions that will grant winners free flights and accommodations to the event.
If this sounds like something you’d consider, head on over to the official forums to fill out a quick form to let the team know!
Source: Path of Exile Twitter