The Apple situation's slightly more complex than that: they're certainly ruthless with their hardware, but it's a bit of a stretch to claim they have commitment issues with their software technologies - ObjC, Foundation and AppKit's been around since the late 1980s from NeXT without serious architectural changes; UIKit'll be around for a while yet; let nothing come between them and their investment in the Apple Compiler Group. (The upshot is that they've sufficiently abstracted hardware away anyway, so hardware changes aren't showstoppers.) If anything, they're more conservative with tossing out the SDKs than most: OpenGL support, for example, is still absurdly piss-poor, even if they're getting better with their GPU driver support. But it
does net you compatibility all the way down their HCL - at the bottom end, for example, is the mid-'07 iMac with the ATi 2600 PRO.
They do give not-so-subtle hints to hand over to them the cha-ching, though, when they EOL old versions of XCode - but that's usually the most you're going to encounter. So works Apple in general.