Then people would complain why their +5yr. card is not supported anymore

. What I think they should do is offer support for pre-HD cards up to a certain release and then stop, with future driver release dropping said support and focusing on newer cards. That "legacy" driver should then only be updated so that it keeps working with newer kernels and xservers. If you still want new features on your ancient card, then look at the open source drivers or something (which is what I think people should do anyway).
Unfortunately, people are likely to also complain if such a thing were done, like when active support for pre-9500 cards was dropped... "why is my card not actively supported anymore?". People will never be happy with the driver.