Whether people like it or not, the only truely 1080 or above sources in Star Trek are the original, unaltered 35mm prints and already up to 4K rendered CGI elements.
Those are the film of TOS, TNG, DS9 and VGR. The 720 footage of Enterprise and 480i-720p CGI that can be fudged a little. And the new movies.
*Everything else* has to be remade in-house by Paramount/CBS and that costs millions of dollars, which *must* turn a 120% profit at least for a studio to consider doing it. Breaking even is not a business model. TNG-R got about 105%, a faliure, one they will not repeat.
They'll making a killing with Star Trek Beyond Bluray and 4K, but that money will go back to the studio in profits and make the decision on how much they funnel into the already greenlit Star Trek 4.
DS9 DVD's don't even move on the shelf enough over it's entire availabliity so far, Bluray making less? no way anyone's touching that.