The official Denon product pages are now up:
The Denon AVR-X4800H is a 9.4 Ch. 125W AV receiver for breathtaking home theater with Dolby Atmos, 8K Ultra HD, DTS:X, and HEOS® Built-in streaming.
www.denon.com
https://www.denon.com/en-us/product/av-receivers/avr-x3800h (you can buy this now, but not the others)
The Denon AVR-X2800H is a 7.2 Ch. 150W AV receiver for upgraded home theater with Dolby Atmos, 8K Ultra HD, DTS:X and HEOS® Built-in streaming.
www.denon.com
I admit, I'm rather puzzled with what they've done with the X4800H. It has the same amplifier and preout counts as the 3800H, which is the same as before, but they've trickled Auro3D down to the 3800H now, and also removed the front HDMI port from 4800H, which was a nice convenience of the 4000-series for doing external(REW, etc) measurements.
As far as I can tell you're paying $800 USD more for... +20W better amplification and +1 rear HDMI port??? This makes very little sense to me, neither of these things are worth $800.
Can anyone else spot any other significant difference?