The Pro Display XDR has about 20 million pixels at 10-bit colour. A 5K display has about 30 million pixels. The 15" Touch Bar-era MacBook Pros all support up to two external 5K displays at 10-bit colour in addition to its internal display, so I would bet they can support at least one Pro Display XDR.
I'm fairly certain that a 5K display has ~15 million pixels, not 30 million. However, your point is still sound.
Not at full resolution...
https://www.apple.com/macbook-pro/specs/
https://www.apple.com/pro-display-xdr/specs/
We won't know for certain until the product comes out or Apple lists support, but the only thing that you linked to that invites questions is the lack of the 6K display being listed in the MBP tech specs. I suspect that Apple simply hasn't updated its product pages for an unreleased product (and there are no other 6K displays on the market, to my knowledge). If the base Mac Pro can make full use of the display with a 580, then at least the Vega-equipped MBPs should be able to drive this, if not the 555- and 560-equipped models.
It's clear that this display is pushing the limits of TB 3. There is so little bandwidth left over after driving the panel that the USB ports on the monitor run only at USB 2 speeds!