As someone pointed out on another forum, this isn't the 30th anniversary of Star Wars. It's the tenth anniversary of Star Wars. Star Wars wasn't finished until 1997 (and again in 2004). Celebrating the preview of the workprints is like celebrating your birthday on the anniversary of the start of the third trimester of your gestation.
As for sci fi conventions, I might go if I could see DeLancie and Nimoy on stage together, but I can't think of a single reason to attend a Star Wars con. None of the personalities in Star Wars seem particularly interesting.