Forgot to catch that point before. The show was still shot on 4x3 film. To go 16x9 you would have to crop the top and bottom of every shot. It could be done but you would be losing material originally intended to be shown, as opposed to movies where going widescreen returns material originally intended to be shown. I believe the plans for TOS-R are to keep the original aspect ratio and just have black bars on the side of a 16x9 monitor.
A ground-up, 16:9, full HDTV presentation of TNG could make CBS some serious money.
Have you seen the remasters of Hogan's Heroes, Knight Rider, The Equalizer or Charlie's Angels in HDTV? They've all been cropped for 16:9. Only occasionally do you miss the top or the bottom; the mask is floating to get the most information possible.
The difference between remastering TNG and TOS is in the amount of work it would take. With some episodes of TOS-R, all they are changing is a couple of minutes of shots. Even in the heavy effects laden episodes, we're still talking less than seven minutes worth of new footage. Remastering TNG will be a much bigger enterprise, no pun intended. Every second of the episode will be new. I can guarantee you if they go to the expense to do a new transfer off the original film stock and then create all new effects in HD, they will crop the picture to 16:9 so that TNG is widescreen. TVs will be widescreen for the foreseeable future and TNG-R would be created to look proper on them. For good or for bad.