to completely re-do all of the post production for 21 seasons (7x TNG,DS9,VOY) of tv. Crazy money and time. At best we'll get an up convertion and not a true HD transfer.
I think Paramount/CBS Home video may test the waters with a compilation of 4-6 episodes.
Originally I thought we may get a fan collective of 12-14 episodes
on Blu-ray with full remastering from original camera negative and all CGI visual effects.
Why should they spend the money on that when they can do 4-6 episodes of TNG [the most popular of the 3 Trek series edited and mastered on standard definition video] on Blu-ray first to see if Paramount/CBS Home video 'gets a nibble on their fishing pole'.
I do not think DS9 will get the same test. If TNG is wildly successful then they may dip their toe in the Blu-ray water with DS9 and Voyager's best episodes.