I think until the security patches stop been released for xp there is no need for people to immediately upgrade but maybe at the very least start thinking about saving money for new hardware. While I like Windows 7, And grudgingly use 8 on my wifes laptop, I don't think there is any need for panic just yet if people are comfortable and still have software that works.
Most businesses that still run XP, and a lot of public services do, will probably be already looking to start upgrading the Windows 7. There is already some systems that are Windows 7 at the hospital I work at in key areas just to make sure comparability and stability is there. After all we don't want an X-Ray machine doing a BSOD on us midway through a scan lol.