Sadly, June 3rd is the day NTRPG Con kicks off, so I doubt I'll have a chance to see any of Roll20's online con in action. I hope it is successful and there are ore of them in the future, possibly even themed (OSR, Horror, Scifi, 5e, etc)
Here's an excerpt from the Escapist article:
According to Roll20, the site, later this year, will be hosting its first "online-only tabletop gaming convention." Dubbed Roll20CON, the event will run for 24-hours beginning on June 3, 2016 and ending at 11:59 (PT) that night. During Roll20CON, gamers will be able to access "an organized schedule of tabletop games" along with a selection of "panels and demonstrations." These events will all be streamed via Twitch. Attendees will likewise be encouraged to play their own games and try out "subscription features" normally reserved for Plus-level members of the site. Assisting Roll20 in its efforts will be the anti-bullying group Cybersmile. During the event Roll20 will work with attendees and sponsors to raise money for Cybersmile.