If the 449/349 pricing is correct then AMD DEFINITELY wont use XDR2, but some new Hynix tech that is in the works.
But if it is the other way round then XDR2 should not be out of the question (not a certainity, but not uncertain either).
It looks like 7900 will be coming with 384-bit DDR5, XDR2 is out of picture. Check the SI thread.