[bigiain]

For devices that _can_ have the OS upgraded - stats seem to show a remarkably high level of upgrading by users, at least for major version numbers:

http://david-smith.org/iosversionstats/

If you scroll down to "Device Breakdown (sorted by Usage)", you see a bunch of devices with 90+% stuck on the "last supported OS version" - 97% of iPad1G on iOS5, 97% of iPhone 3GS and iPod Tough 4G on iOS6, 91% of iPhone 4 on iOS7. Even including thise devices, they're showing 75% on devices on iOS8 and 20% on iOS7.

I'm in the "left behind" category - with both my iPad1 and Mac Mini single core being "stick" at iOS5 and OS X 10.6 respectively. Im somewhat disappointed at the lack of patches for the known security holes in iOS5 - especially since those numbers still show over 3% of the iPads in use are not upgradable past iOS5...