Reruns isn't going to be the only factor. There's streaming services like Netflix. Odd though, that Netflix hasn't replaced the older SD version with HD, while other programs like Hulu have. Perhaps when TNG is finalized in HD that's when networks and streaming services will offer more of TNG in HD.
As for DS9 and VOY, well, I suppose we'll find out about that sooner after TNG is finished. The last time I'm aware any of those shows aired on a network was as far as 2008 on Spike TV, and they only acquired the rights for VOY in 2007 so it was only for a year more or less that they aired them.