TNG's FX are pretty consistant on the whole and don't really need the overhaul TOS got. Looking at the various shots of orbiting starships across TOS-R, TNG, DS9 & VOY, they're quite uniform and compliment each other.
Not having a HD TV myself yet, does TNG really look that bad when upscaled from Standard Definition? There must be many shows from the late 80's/90's, when everything was done on videotape, which can't be improved on because the film rushes were not kept (to say nothing of studio based sitcoms done entirely on VT). For those, we're really looking for a time when technology can artificially create extra lines of picture information.