No one has
to do anything. Least of all when it comes to their computers. No one is required to use Windows 7 just like no one is required to stop using Windows 3.1.
Just as with any "upgrade" there are advantages and drawbacks with Windows 7. The general consensus is that it is vastly superior to Windows Vista and an all around neat bit of work; I haven't seen or heard of any "absolutely must have" features, though. Many users, myself included have no intention of upgrading in the near future; Windows XP works just fine for me and so long as Microsoft continues to issue security patches for it, I see no reason to change.
The long and short of it it this: your computer is your property. You own it and may do with it as you please. If you wanted to, you could dump Windows entirely and install Linux, BSD, Plan 9, or some other operating system and no one could say a thing against you.
(Note that the whole notion of "Trusted Computing
" may eventually make that last statement false.)