I don't see the benefit of just re-mastering some of the episodes -- that might be enough to put on home video, but it wouldn't be enough to widely syndicate. If CBS is going to make the investment of getting a team together to re-scan the negatives and build CGI assets, that's an awfully big investment to make on such a limited prospect as a "Best of" DVD or Blu-Ray.
But as an advance? i.e., they put out DVD/Blu-Ray of, say, BotW/Family and Unification (5 episodes, one - Family - practically a "bottle show" for effects). They then plough that money back into the major remastering effort, with several major assets - the Ent-D model, Borg Cube model, Warbird and some others - now effectively paid for, and some major stock shots fully rendered.
Well, I assume they'll put out the remastered episodes pretty soon after completion, but there's no way that assembling the team and getting the infrastructure together only to do five episodes is the best way for CBS to spend their money. A home video release would take some time after completion to be put together and released. Then, CBS would have to go back to square one and put together everything again
. That doesn't sound efficient or cost-effective to me.