Microsoft state

After careful consultation with our customers and industry partners, we’ve decided to proceed with our plan to stop selling Windows XP versions in packaged product (retail) on June 30, 2008. We plan to provide support for Windows XP to our customers under the mainstream support policy until April 14, 2009, and under the extended support policy until April 8, 2014.

Windows XP: The facts about its future

Q & A From Microsoft
The lifespan of every Microsoft product is carefully mapped from launch to retirement. Windows XP is no exception. We do this to ensure our customers always get the most out of their PC experience. (Read about the Windows lifecycle policy.) Although it won’t be sold in stores, Microsoft and its partners will continue to offer technical support for Windows XP for months and years to come.  
In Fact, Microsoft plans to support Windows XP until 2014 We’re proud of Windows XP, a product that’s empowered and entertained hundreds of millions of people in the last eight years. But technology doesn’t stand still. And neither can we.

What’ll happen to Windows XP after June 30th 
On June 30, 2008, Microsoft will stop distributing Windows XP as a stand-alone product that can be bought shrink-wrapped in retail stores. We’ll also stop sending it to Dell, HP, Lenovo, and all the other major PC manufacturers to sell on their PCs. This is called "End of Sale". 

That said, Windows XP isn’t going to disappear overnight.

You may still see copies of the software—or computers preloaded with it—for months as stores and PC makers work through their inventory. Also, system builders can continue to sell PCs with Windows XP until January 2009. Finally, Microsoft recently announced that computers with limited hardware capabilities—devices sometimes called Netbooks or ultra-low cost PC s (ULCPC)—can carry Windows XP Home until June 2010. (Read about the ULCPC program on Microsoft PressPass.) 

I’ve heard I can get Windows XP for businesses past the June 30 deadline through something called "downgrade rights." What are those exactly? 

For businesses that rely on Windows XP, there’s still a way to get it. When customers buy Windows Vista Business or Windows Vista Ultimate, they have the right to move back to Windows XP Professional via what we call "downgrade rights." We’ve been working closely with our industry partners to develop new programs for business customers interested in exercising these rights.

For more details on downgrade rights see:http://www.microsoft.com/downloads/details.aspx?FamilyID=4f4b3cfd-7f4e-46cb-8117-8275f7683d3f&DisplayLang=en

My customers and my business rely on Windows XP. What’ll happen after June 30th  if I have technical problem?

We understand some of our customers aren’t ready to upgrade their PCs to Windows Vista. Although Windows XP will disappear from stores, we’ll continue to offer Extended Support for the operating system for six more years We understand some of our customers aren’t ready to upgrade their PCs to Windows Vista. Although Windows XP will disappear from stores, we’ll continue to offer Extended Support for the operating system for six more years, until April 2014. PC makers can also provide technical support for PCs. Please contact them for more information.  

For more details, see Microsoft’s Support Lifecycle website.

I’ve heard about two types of Windows XP support—"mainstream" and "extended". What’s the difference?

Mainstream Support delivers free security updates and bug fixes to all Windows customers, as well as technical assistance for customers who purchase a retail copy of Windows XP (i.e. a shrink-wrapped, not pre-installed, copy ). Mainstream Support for Windows XP will continue through April 2009. Extended Support delivers free security updates to all Windows customers. Customers can also pay for support on a per incident basis. Extended Support for Windows XP will continue until April 2014 . New bug fixes require the Extended Hotfix Support program.