^ Obviously this doesn't apply to *early* episodes like WNOHGB and Haven, but in general, some of that might be due to the uniforms themselves. If a uniform is worn repeatedly and washed, over and over, it will fade. This is why characters like Beverly, who wore the same blue uniform for the series run, seem to wear a much darker blue than, for example, Picard in "Tapestry". In that ep, his uniform was brighter, because it had never been worn before.
As for TNG-R, we will probably get a Fan Collective or two in HD, but I doubt any more than that. There's simply too many episodes. They managed with TOS because it was only three seasons (and was all shot on film from the get-go). TNG would require many more years of work.
The next Trek series to make it to Blu-Ray will be ENT. That's pretty much *already* in HD (it's been shown that way on TV).