Trailers don't always represent the final colour grading. If they were fixing the colour issues, it's possible, maybe even likely, that the trailer from a year before its release would not feature this. So, personally, I'm not using that trailer as proof of anything, they probably just used whatever footage was onhand.

No doubt, the 2004 master is being used again, as in that particular scan. However, films usually get tweaked visually for BD compared to the same master on DVD--sometimes its just a matter of adding some DNR, sometimes its crushing the blacks a bit more, sometimes they do a better colour pass; depends on the film.

But, based on LFLs history of releasing crappy transfers, being okay with them, and re-releasing them year after year, I'm not betting on any significant new work for the OT transfers, although I do think the hues and levels might be slightly different--not corrected or better, but perhaps slightly different--just because each pressing and broadcast tweaks things ever so slightly. There's no need for DNR, since Lowry basically did that, and Lucas not only personally supervised the transfer but also has seen it screened a number of times since. I have to believe that if he actually noticed Luke had a green lightsaber or all the other issues that he would have pulled the release and issued a correction right there. So, either he's never noticed, or he's never cared, in either case we would be getting the same thing. That's my view, anyway.