Except that a lot of sensible people don't install the final updates for any given Apple iDevice that's going out of support, because it's often so slow as to make the device unusable and Apple have got strong anti-downgrade protections that stop anyone from rolling back to the previous version. Nice bit of forced obsolescence.
Running iOS 7 on my partners iPad 2 is fine. The biggest performance issues with it are websites that are more and more complex than just a few years ago when she got the iPad. They lag like hell.
I understand why Apple makes downgrading so difficult but I agree it is a real pain in the ass and wish it was simple to do.
It'd be pretty terrible if it didn't run properly on there, since as far as I can tell Apple are still making and selling the iPad 2. I'd be curious how the iPad 3 is doing since that was discontinued a year or so ago.