Apple just released an update of the list of old computer models flagged as obsolete on September 15th:
iMac USB 2.0
iMac (17" Flat Panel, 1GHz)
Xserve RAID (SFP)
So, after this date, you will not have the possibility to repair those models in a certified Apple center, as spare parts will not be available anymore (impossible to order new ones); but you should still be able to find them on internet from third-parties or Mac users.
