So can I interpret this as Mac user has never been able to "jump" upgrade? say from 10.3 to 10.5 or 10.6 to 10.8?
No, the Mac App Store is new. You could have gone from 10.0 - 10.4 if the hardware supported it. I took an old G3 Pismo from OS 9? to 10.3. 10.4 wouldn't install on it since it didn't have firewire and I didn't feel like jumping through hoops.
My friend went from 10.3 on his PowerBook to 10.5 and then went from 10.4 to 10.6 on his MacBook. There will be a way to get this in some sort of physical form and you should be able to put it onto any 64bit intel system at the very least. I don't have a working Core Duo to test on so I can't say if they can run 10.7 or now.
