I cant remember number of devices - but it was somewhere between 10-15% of users that would be stuck with old version of my app - that would work with Android 4.0.3 and up to but not including 4.4. Everyone else, from 4.4 and up, is along for the upgrade-ride, new features and all.
I just allowed in the release dashboard for older versions of my app to continue to serve those with older versions of Android. I could do that, as there was no breaking changes as such - however soon I know those without Android 4.4 or newer will lose reason to use the app as I cannot push new features to them.
But that is fine. The app I am discussing here is free, open source and I got no paying customers complaining about their 6 year old phone won't work with my app. You'd be surprised how many think very old gear should work with very new services...