Those customers will find that Microsoft products are not working for them anymore.
Office 2010 does not work on XP.
IE8, never mind IE9 and IE10 does not work on XP.
Visual Studio 2010 does not work on XP
All of Microsoft's games division do not produce games that work on XP
Microsoft Hyper-V does not work on XP.
Do you see a pattern?
Microsoft director Stella Chemayk:
"If you still have some PCs running Windows XP and Office 2003 in your organization," Microsoft director Stella Chernyak wrote in a post to the Windows For Your Business Blog, "now would be a good time to start migrating them to Windows 7 and Office 2010."
So Microsoft's official policy is "upgrade your XP". Not "let's find more excuses for customers to avoid upgrading from XP".
A typical business takes between 9 and 18 months to upgrade all of its machines to a new OS. This means that by the time VS2011 ships, either all of your customers will be running Vista+, will be in the process of upgrading, or will have resigned themselves to running an OS that simply isn't suited to modern day use and which Microsoft will have well-and-truly left on the scrap pile.