It would be a disappointment if it did use the same pair and not a new and improved pair as I've heard that almost everything else about the X's are a downgrade to the original. People have said that the cable feels a lot worse and tangles easily and the build quality overall is a whole lot worse. I would really hope that the sound quality is better with a new and improved driver if they are a let down in so many other areas.
I see. That's a shame.
Not to defend AT, but they could simply put the same drivers in an improved housing and the new headphone would be an upgrade over the old that way, too. If they were to bother to do that.
In the early 2000s I was a huge audio technical fan. They could basically do no wrong to me. These days I couldn't be more disappointed in them. They seem content to ride the (completely unwarranted) success of the ATHM50x. They otherwise put out complete garbage or sort of mediocre stuff (the R70X is okay, but nothing special). The MSR7 is fine-ish if you like that signature. But they aren't close to the top in any category other than lifehacker recommendations (they seriously once called the M50 the best headphones in the world).
In addition to the M50(x), their AT2020 microphone, I suspect. It is widely recommended by everyone and his grandmother just like M50x, but sanely within its price bracket ($100 and under), from what I've seen so far. Also sells like hot cakes with weed in them, oh hoho.