My "completist" feature—a comprehensive review of every episode of every live-action Star Trek TV show and film—is now up for your reading pleasure. One point I make that's of general business interest even to non-geeks is that the commercial failure of the final Trek TV show is very much a relative matter. The show in question, Enterprise, aired on the then-new UPN network (since merged with the WB to become the CW) which aspired to the kind of mass audience that broadcast television could still count on in the 1990s. But compared to a modern-day cable television show, Enterprise was extremely popular: "The highest-rated Mad Men episode ever, the Season 5 premiere, drew 3.5 million viewers—a mark that even the failed Enterprise series beat in the majority of its episodes."
Which is just to say that if you think of Enterprise as representing the hard core of Trek fandom then it's clear that there's a very healthy audience out there for a Star Trek cable show. Of course you could make a Star Trek show on cable that everyone hates and it would fail. But to succeed, all you would need to do is make a show that hard-core Star Trek fans like. The tension between trying to make something that appeals to the fanbase and trying to make something that recaptures the mainstream success of The Next Generation would be alleviated.
I find it really hard to believe that if you asked Jeri Taylor and Manny Coto to forget about JJ Abrams' trashing of the continuity and devise a new show designed to make Trek fans happy and designed to operate with basic cable budgets and audience expectations that you'd have a huge hit. Everything about the economics of the television industry—from the falling cost of CGI effects to the general shift toward fragmented audiences and niche programming—is working in favor of Star Trek returning to TV. And of course you could do it like a modern-day TV show, with short seasons and season-long plot arcs. Deep Space Nine was working toward that kind of more sophisticated approach, and during its best stretches it offers the best Trek that's ever been aired. It could, and should, happen again.