Carroll, the Domino XL will use 12 and 14mm widths in addition to 8 and 10mm. Also, tenons will be available up to 140mm in length, I believe.
My friends in Europe agree with you, that the XL Domino will make far deeper mortises and will use cutters up to 14mm dia.
What is still less clear to me is if the XL will use longer 8mm and 10mm bits. Half of 140mm is 70mm, which would seem ambitious for a 12mm cutter. But it might well be practical to make 8mm mortises deeper with a longer cutter than the current Domino 500.
It also is unclear if for the XL Domino there will be 8mm and 10mm tendons longer and wider than the current ones we use with the Domino 500. The current 8mm Dominoes are all 22mm wide, in a choice of 40mm and 50mm length. Currently the 10mm Dominoes are 24mm wide by 50mm long.
Perhaps the XL Domino will oscillate more, to use even wider tendons and still allow the extra width like current style. Probably a 12mm and 14mm Domino would be best wider than 24mm. Personally I expect the XL Domino machine will require a dedicated set of cutters, possibly with shanks more like 12.7mm than 8mm just to be robust.