From the appearance of the lightsabers and their associated flashes, I think this is still essentially the 2004 master, but a 'non-screwed-up' version of it: what the scan looked like before its color and contrast were later ruined. It could have been upscaled to higher resolution to do additional work more recently.

Or, it could be a new scan initially made for 3D re-release, with the '04 changes put back into it. Either way, the quality will surely be better than anything currently available, so if it gets a Bluray release, it will make a good source for improved Despecialized Editions later on (in combination with Team -1 scans of the original shots). I'm not convinced there's really more to be excited about than that, though I suppose there's a vague possibility of them making a branching version that follows the original edit by taking out the most obvious changes.

Hmm . . .