The dates in the Wiki suggests that Microsoft would only sell one operating system at a time, at least only one per customer group. Is that really how it officially works, that whenever they have a new Windows release, major manufacturers are expected to switch over within two weeks and the only computers remaining to be sold with the old version are surplus inventory?
It should be noted the article says support was planned to be discontinued on January 16, 2004 but due to a large number of users Microsoft extended it to July 11, 2006. Of course it doesn't mean new systems were shipped with Windows 98 or 98SE in 2003/04, but if it had been completely superceded already in 1999 or 2000, there would not have been that many users still running 98 to extend support by more than two years.