I did find it a bit weird when they announced the DLC that they were referring to as a remaster and not a remake/re-imagining, since all the re-releasing tracks they have done to this point have been remade from the ground up. When I saw the trailer in the direct I did not really notice that these tracks were not taking the remaking style. But after watching the trailer again after the fact, I can definitely see that this does seem to be a remaster like they hinted at and not a remake. While they still look a lot better, it is a bit disappointing that we will not be getting that same standard of quality that we have previously gotten. But I guess we now know why they went with the price of $25.
I think the one thing I'm most worried about id the potential lack of anti gravity in pretty much all courses if they are just remastering. But hey I bought the game finally on the Switch since I'm still hyped. (Have MK8 on Wii-U)