Even when Trek actors do come to a larger convention, they don't pull the numbers that you might think.
One of the indelible images from a con I went to was Tim Russ dozing off at his table all by himself while a line 60 people long waited to talk to Bruce Boxleitner.
It's tough going to these conventions, where the one-time King just isn't popular anymore.
I think the right phrase is "AS popular." There was obviously enough support for the convention organizers to ask Mr. Russ to attend, and enough reason for Tim to bother showing up. However, it was pretty clear he (and Brent Spiner) weren't in the top tier anymore.
Couldn't agree more. Shatner and (formerly) Nimoy? Still top drawer. And in this country, Patrick Stewart would be too, but that's it. Everyone else, from George Takei to Tim Russ, from Jonathan Frakes to Avery Brooks, is a mid-length queue at best. Probably still make a tidy profit on overpriced autographs but they're hardly the main billing for the event. Those (like Kate Mulgrew) who draw a crowd today do so for more recent work. When I met Armin Shimmerman at Collectormania he told me he was signing nearly twice as much Buffy stuff as Trek stuff and at that point Trek was still on the air.
I've noticed the same decline with Stargate, my other big fandom. The guests, cosplay, and merchandise has waned considerably since Universe came off the air. There used to be a guarantee of 3 or 4 SG teams with rubber P90s at Collectormania, or LFCC; now, many have moved on. Ditto BSG. Not all bad, of course, Twilight went the same way.
The big mega-conventions are the order of the day and they are heavily influenced by what is on TV and in cinemas now. The guests, costumes and stalls are Game of Thrones themed, or Hunger Games, or even smaller but going concerns like Gotham. If you got the cast of the nuTrek series in, particularly the big names, they'd be popular because they're current. But a lot of convention goers today were barely in primary school when Voyager was on. They're just not that interested.