Microsoft has confirmed what had already been hinted at. They will offer downgrade licenses for Windows 7 to go back to XP:
Users can downgrade to Windows XP and Windows Vista from Windows 7 via OEMs for 6 months after Windows 7 General Availability. For customers and businesses running Windows XP, Microsoft still recommends an upgrade to Windows Vista before moving onto upgrading Windows 7. If the user needs to run Windows XP Professional on new PCs and if they are running Windows Vista Business or Windows Vista Ultimate already, they have the automatic right to downgrade to a previous version of Windows for the life of that PC and the downgrade media may be obtained by an OEM for Windows XP for the service life of that PC (OEMs can choose to provide downgrade media).
The direct actual post is here.
I don’t care what they say it doesn’t give inspiration for the new OS when before it comes out the topic is downgrading.
Da Techguy's (no longer backup) Blog 
they did this back when XP was even out, allowing downgrades to 98/ME. Nothing new.
However the promotion of the retention of XP two operating systems back is rather amusing. How many people do you thing decided to downgrade to ME and how many people actually would use the downgrade?
In this case I suspect it will be much larger.
Of course since XP is the os of choice of those cute mini computers I suspect it will live long and prosper for many years.