I'd be surprised if very many people with Office XP are running out and buying 2003. This is mostly for people still running 97 or 2000.
And I hasten to point out (for the umpteenth time) that it's not the average consumer but businesses that MS is targeting. For example, my company tends to use not the current version but the previous version, then they only upgrade every other version. We're still using 97 but will upgrade to XP next year.