I buy a new computer when I want to, not when Apple tells me to. I've just updated my 3 year old Mac Book Pro and my 18 month old iMac to Snow Leopard for £39, it would cost over £2600 if Apple were to go with your suggestion.
And no, I don't want to "support" Apple. I like a lot of their products and buy the things I need (and often some I don't need) As a company they are no different to Microsoft, Dell or any other multi billion dollar corporation. I certainly don't have the emotional attachment to Apple that a lot of people on here seem to have.
It sounds like a lot of people here (in this thread) would support such a move (based on the contents of this thread). How many Mac users actually upgrade versus just buying a new computer. It would seem those that are here would be more inclined to upgrade, but what about the average user?