Seriously. My current (and only) machine is more than half as old as XP is at its core, and I'm not about to drop over $100 on it just to replace a still-perfectly-usable OS. Even after MS finally ends extended support for XP, I expect I'll still have it as a dual-boot somewhere, for legacy purposes. Hell, I might even try building an old-school 98 machine someday for the fun of it.
I think Fury's point is that if you're buying/build a system or looking to upgrade an OS. If you have an old machine and it's hardware is fully utilized by XP, then no, there isn't a compelling argument to upgrade just for the sake of doing so.