If you look at the fan CGI work being done in these very forums and elsewhere, I think there's a distinct possibility that at some point in the future we'll get fan remasters of DS9 and VOY - and probably even a better remaster of TOS. The technology is getting to where non-professionals are able to do work that surpasses what pros could accomplish a few years ago, and fans have the advantage of slave-like devotion an dedication to detail. Of course, the biggest hurdle will be copyright enforcement by our friends at CBS/Paramount...
Well, they would also need access to all the filmed elements and the manpower to redo the post-production process from scratch. This isn't just the matter of the effects, it is a matter of how the 24th century shows were put together.