Not sure I'd pay a premium for it, but a long-forgotten show that I'd get on blu-ray is Almost Grown, a show by David Chase that aired for half a season or so in the late 80s. It starred Tim Daly and Eve Gordon. The music rights would no doubt hold it back, but if anyone could handle it, it's Chase.
I'm not sure Star Trek TOS would be a good fit for 4k. The blu-rays are incredible, and we're kinda at the limit of what high resolution would allow without detracting from the show. It's already obvious that the stunt people are not the actors.
Minus the remastered FX, there is every reason to believe that the HD versions of B5 currently on HBO MAX will come to blu-ray. Warner has been very good about releasing their shows on disc.