WOW......now who would have thought I could have been right all along hey !!! Ryzen 3xxxXT was quite obviously N7P an enhanced and optimized version of N7 bring upto a 7% increase, ring any bells, and there is no 7nm+ (N7+) for AMD, Lets call the XT's secretly Zen3...or Zen2+ if you prefer, its AMD, they can do what they want.
And as the video shows, they are waiting for TSMC to start producing 5nm+ later this year, so you wont be seeing any Ryzen 4000 CPU's until 2021, makes perfect sense to me, as Ryzen 5000 isnt due until 2022, the way its always been on there roadmap, what........were they not going to release nothing in 2021.
Now lets wait for the news where they say they tried, but they couldnt make it fit on AM4, so a socket change is required, ie new motherboard, and when everyone starts moaning,
AMD will just say "well we did say we would only support AM4 until 2020" its 2020 now, next year if you dont like it, you can always move to intel and there further enhanced 14nm chips.