According to TechARP.com all systems (running Windows Vista OR Windows XP) that are purchased between June 2009 and January 2010 will have an optional Windows 7 upgrade.
On top of that, Windows 7 buyers will have the option to downgrade to either Windows Vista (why would you do that?) or Windows XP.
So, let’s assume you buy a PC right now, but you don’t like Vista and downgrade to XP, then you will be able to upgrade to Windows 7 for free, once it has been released.
Warning: Should you buy a PC that has Windows XP pre-installed, then you get no free upgrade to Windows 7. The reason is that those PC’s will not have a Windows Vista COA (Certificate of Authenticity).
Warning2: The XP downgrade (from Win7 to XP) will only be available for a limited time. Now this might not be so important for endusers, but it’s a crucial information for businesses who decide that Windows 7 is just not worth the trouble.