It's impossible for them to support a 10-bit 6k@120Hz monitor with current hardware and keeping the old one around would be embarrassing. The Pro 5k will probably sell better/be more profitable anyway.
On the other hand this is the company that sells a Mac Pro for $7k and it comes with an M2-based chip...
The 6k XDR has been replaced, apparently they've got something coming for the Mac Pro. I don't know why it wasn't the Mac Studio update last year. Maybe we find out at WWDC this year.