As Windows XP nears the end-of-life though, it is Microsoft's policy to release a final service pack to wrap up all those hot fixes and patches released over the past few years. A Sayonara Service Pack, in other words. What this means is a much easier patching process for those who still want to stick with Windows XP. Almost a thousand Windows XP updates in a single download.

It doesn't matter if you are still using the original, unpatched Windows XP or Windows XP Service Pack 2. You can upgrade directly to Windows XP Service Pack 3. You can also slipstream Service Pack 3 into your Windows XP installation media. This allows you to install a fully-patched Windows XP SP3 without going through the ardous process of downloading and installing the many, different updates.

http://www.techarp.com/showarticle.aspx?artno=444

I could see myself using Windows XP for at least 2 years+.