Speaking as a 31 year old who has been to around 14 Swancons over the last 15 years, yes, the 18-30 year olds are coming to cons. I am certain I've seen younger people than myself at this years Swancon.

I think the way to recruit them to cons has changed since I started going, but not by much. Pique their interest, and get them to come in groups. Offer them lower rates for a first time appearance, and maybe even give some sort of incentive for recruiting new people.