I don't know what Apple web site you've been looking at, but it is still available at the Apple Store for $99. For 30 more greenbacks you might as well get the Mac OS X, Mac OS 9, Developer Disk bundle.
FYI - if you have Mac OS X Beta on that machine, it won't run after 15 May, 2001 anyway.
If you plan on installing Mac OS X, you'll need to wipe the drive. It won't successfully install over the Beta.
Not all users of older hardware have even upgraded to 9 yet, so it will still be for sale for some time I imagine. But I am not surprised that the web page shows OS X, because it is the current and future of the Mac OS.