Seriously? Apparently you guys can't see the forest for the trees. Normal consumers replace their machines every 2-3 years. Apple knows this. They are steadily progressing their business model to where new, heavily advertised features will *only* run on the latest hardware. And why wouldn't they? That's where the profits are.
I'm a "normal consumer" and I've averaged four to six years out of every Mac I've bought since the nineties. My last iMac was still running a current OS, no problem, after five.