Not quite the same though, is it?
Apple's transitions have all come along with forward paths and backward compatibility. For the shift from 68000 to PowerPC, a 68000 emulator was bundled (and, reputedly, used internally by much of the initial versions of the PowerPC OS) that allowed old applications to continue running. The APIs stayed much the same, so there was no discontinuity in development skills. If you wanted to target Macs, you continued with QuickDraw, etc.
The switch to OS X came with the idea of carbonised apps — limit yourself to a subset of the existing APIs and build correctly and your app works not just now on OS 9 but natively on OS X when it comes. And OS X had an ability to run OS 9 as an app to run older apps. Although Carbon was a concession Apple didn't seem happy about, it was a first class member of the software stack up until 10.5.
The PowerPC to Intel switch was like the PowerPC switch. An emulator for old apps, all APIs to remain the same.
Conversely, the switch from Symbian/MeeGo to Windows Phone <version number as yet undisclosed> is announced to be a complete discontinuity of APIs and software support. The old Nokia obviously thought that sort of thing was a bad idea, hence QT to ease from Symbian to MeeGo or wherever they might end up. With the Microsoft tie-up, even QT is out of the window, per Microsoft's decision not to allow unmanaged code. Per announcements so far, we're not even going to get an emulator for older Nokia apps as Palm supply (or supplied?) on WebOS.
I really think the main reason people are concerned about an OS being dead is that they can't take their software with them and, more than that, if the APIs are about to go then the developers vacate immediately.
You're completely right about free stuff though. Giving away free can mean either that people don't want a thing (ie, it isn't selling) or that they do want it (ie, it's a good inducement).