I have no confirmations. Everything I am about to say is gathered from sources I've skimmed over time. As far as I know, the ride isn't changing its thrill factor at all. The only thing I heard in terms of improvements is that they might add things they didn't have the budget for. From what I hear, Japan's will be grander and have a larger budget. As for motion sickness, I heard they might install "air-bladders" into the Enchated Benches. These fans will create a constant flow of air that decreases the chances for motion sickness and disorientation. I'd keep the ride the same too. But it bothers me to no end that Fawkes is not inside Dumbledore's office.
We in Orlando are so spoiled lol I'm thinking to myself, WHAT?! Japan is getting a better FJ?! Even though we already have Diagon Alley. But I agree, as a Potter Fanatic, Fawkes should definitely be in Dumbledore's office! And an AA Basilisk, Troll or Fluffy would be amazing too!!!