I'd love to see this stuff in HD. As already pointed out there are FX problems. It may not be all that bad b/c the models were filmed on film (that sounds redundant). It still seems like it might be a little more expensive than I think Paramount/ CBS would be willing to spend.
I'd really love to see all Trek upgraded for HD. I don't know if it will happen though.
For now, I'll settle for the movies. I'm going to guess that TMP might be the easiest b/c of the work that was done during the special edition.
I'm going to guess that everything from WOK up is going to need some work where the FX is concerned.