Versatile, Stable and Popular
Along with being the dominant operating system on low-end laptops, with the increase in capacity of portable memory devices such as USB flash, Windows XP has gained a new lease of life as a portable operating system.
As floppy disks have become anachronistic, USB flash devices have taken their place; being able to boot a PC from a floppy disk was a key way to resolve issues in older versions of Windows, and with most PCs it is possible to boot and install XP from a USB device.
This requires a stripped down version of Windows XP to be setup and installed onto your USB device along with whatever utility you plan to fix your boot issue with, such as an anti-virus app. Windows XP can be run from a USB flash device as small as 256 MB.
Similarly, it is possible to setup a bootable CD or DVD to run Windows XP on your PC.
As long as the operating system supports such versatile methods of issue resolution and power to low-end laptops, Windows XP will be around for a long time yet.
XP might not outlast Windows 7, but it will certainly outlast Windows Vista.