The "superstations" existed because they exploited a loophole in the FCC regs and the law at the time. They were legally just a broadcast station and a cable company carrying them was no different than a cable company that pulled in a broadcast station from another town. The catch was they were not entitled to be paid for the signal, and had to live on ad revenue alone.
Eventually the system caught up with them and they all converted to being regular cable channels. Such as WTBS becomes TBS and WGN becomes WGN America.
What we are seeing now is the death of the "general rerun" channel. All have about the same formula. Off-network reruns, with an occasional "original" series. The same reruns over and over and over and over.
With the networks producing less and less filmed shows, the stream is drying up. Plus streaming can provide (commercial free and on demand) similar or better fare, while the diginets are 99% the same M-O, off-network reruns, albeit generally a little older, and the diginets are free.
I think the next 5-8 year will see plenty of attempts to convert these types of channels into other things (personally I think News Nation is a stupid idea), merge these channels, or simply put them on auto pilot without any attempt at being relevant. Several will shut down.