|"I guess we'll have to wait and see to be sure. If you have to first install vista and then 7 ...."|
You got that right with the exception of the wait & see part.
There is no waiting or seeing. The rule is simple: You need a qualifying OS installed & activated in order to use the Windows 7 "upgrade" media for a full install. In other words, if you have a blank disc, you cannot use an upgrade media to complete a full install, if otherwise, you're good to go.
Now, as far as performing an in-place upgrade from XP to Windows 7, there's slim to no compelling reason to carry all the system clutter from XP to a newer OS. But anyone that prefers to do that, can sure do. Insofar as they are prepared to do an in-place upgrade twice: one from XP to Vista & then again, from Vista to Windows 7 to complete the XP-to-Windows 7 "in-place" upgrade migration on their system.
So far, the only
alternative workaround to a double install is to use a program like PCmover for the in-place upgrade. And this approach involves the use of an external storage media of some sort to store the PCmover image created for the XP installation, which will then have to be restored after Windows 7 is clean-installed on the same machine so as to merge the files & programs settings from XP to the Windows 7 desktop installation.
Windows 7 News!