Not to be a troll or anything, but the one problem that I have with Apple's policy of "discontinued OS's" is that they are the only ones that implement it. I can go put Redhat 5.0 linux on a new Intel/AMD system. Hell, for that matter you could put Dos 6.22 and Windows 3.1 on if you really felt like. Sure, it's of no use, but it's a freedom that you have, even if you don't exercise it.
As trivial as it seems, it's an artificial limit imposed by Apple, and the last thing that any good American likes it a limit put on their freedom. Apple doesn't have to support OS 9 at all- they don't need to release updates, release drivers, or patch any bugs. If Apple came out with a bluetooth keyboard and it didn't work under 9, nobody should complain because it's a discontinued OS.
That said, here's why Apple is doing it:
People would complain. Let's just say that Apple keeps shipping 9 on the new Macs in January. Let's say that they upgrade to Radeon 9700 Pros. So, you're average Joe Schmoe boots into 9 in order to install something like Quake 2. OS 9 doesn't have a proper extension for it because Apple never made one since it's a "discontinued os." So, Joe whines and kicks and screams because Apple shipped him a computer that has an OS that doesn't fully support his new hardware. So, Joe takes Apple to court.
Sound unreal? Maybe, maybe not. As trivial as it may seem, it takes double the money, double the time, and double the man power to support two OSs vs. one- money, time, and man power better spent elsewhere.