This car ought to be on sale now.
The beautiful styling of the XK, combined with crushing performance and 42mpg economy would surely be too good to resist, the ugly 635d with it's awkward styling and horrible ride wouldn't stand a chance.
Factor in the usual Jag refinement and ride/handling and you've got a winner.
Suprises me that the launch of XK D hasn't been rolled into the launch of the same engine in the XF and the new V8's in the XK.