It'll be upscaled from the masters. Yes, that'll suck, but at the same time digitally cleaned up footage from the original reels should look MUCH better than the copies of copies we've had on TV and DVD for the past god knows how long.
There are no "reels" to remaster. Upscaling videotape will never look any better than "Trials and Tribble-ations" did on the TOS blu-ray. They have to reedit the original raw footage again or it won't be even close to HD. Apparently they think they've found a way to make this feasible, so we'll see what happens.