What Microsoft do not want you to realise is that Windows 98 will continue to work and function normally beyond this date. It is highly likely that if you bought your hardware at the same time as Windows 98 then you probably will not be able to use Windows XP on your old 98 machine anyway.
but, if you have 98 running on an offline machine, and your just using it for playing classic games or wordprocessing, and it aint broke, then don’t try to fix it.
If you want to use the internet safely, and take advantage of modern applications, then check your hardware is on the Hardware Compatibility List for Windows XP before running out and buying it.