The only thing that needs to be done with DS9 is a good digital transfer to Blue Ray.
They would have to remaster the show for that to happen.
As has already been pointed out, since DS9, TNG and Voyager were edited on videotape - and had their EFX done on videotape - it is literally impossible to show them in HD, or to release them on Blu-Ray.
A remastering is *required* for either of those to happen. It's unavoidable.
And that's all well and good. Most of us saying no to remastering just want to make sure that the show stays the same and doesn't get the Star Wars treatment.