Oldies would definitely put this on their calendar in between family/work commitments if they were made aware of it, liked the bands, and if the fest seriously played up the "once-in-a-lifetime" and "nostalgia" cards for those aging rockers.
Has Mike looked into paid adverts via Facebook? You'd be surprised at how many people can be reached that way. I know for example Scarab Promotions in Calgary (Noctis fest) started doing that 2 or 3 years ago and it's pretty much sold out every year since then (500+ tickets sold in smaller venues, close to 1000 in the larger halls) and this is talking bands like Root, Metsatoll, Manilla Road, Manegarm, Cynic and Grand Magus, all of which are one-off gigs. A few local bands here have scored distrobution deals with labels for their albums using that route as well.
That being said, you can't underestimate the youngsters and their internet connections in this matter! More 20-something-year-olds than ever are into obscure and underground metal from the 80's and such. The guys from Gatekrashor, Demon Bitch and Borrowed Time and my own band Gatekeeper are living examples of that. Lots of my friends love the lineup for this year's fest, but they're all paying off student loans and pouring money into their own bands and can't afford the $500 plane ticket from Canadia. Gotta find the kids that dream about Keep it True festival and advertise this fest as a closer, more affordable alternative because the line up is certainly comparable.
I'm glad to hear that the fest is projected to sell out, but let's not get caught up in wishful thinking too quick here