The upcoming iOS 10.3.2 will be an unprecedented one, and not in a pleasant way. Apple is doing something very unusual in that it appears to be shutting down support for older iPhones in the middle of iOS 10's "shelf life", so to speak.
Both beta iOS 10.3.2 releases available are skipping 32-bit devices altogether, which is out the norm. No former iOS release, beta or final, has ever done this unless it was a dedicated bug fix for a specific device.
This means the 10.3.2 update won't reach an approximate 43.7 million iPhone owners who still use the iPhone 5 and iPhone 5c. These are the last 32-bit iPhones to run iOS 10, and they will be forever stuck on iOS 10.3.1. Apple is keeping quiet about this, but the writing's on the wall.
Granted, that isn't a bad place to be, and the fact these ancient models run the latest operating system is a little miracle in itself (cough, Android). But it looks like Apple won't see them all the way to iOS 11. It's also setting up for the somewhat unfortunate possibility of cutting off device support mid-iOS cycle in the future.
The iOS 10.3.2. update includes a fix for third-party virtual private network apps. New SiriKit car commands are now working, and some bugs have been exterminated. That's what the beta updates contain so far.
In case you'd like to inquire about our approximation of the number of iPhone 5 and 5C owners – BMO Capital Markets estimated a 715 million total iPhone installed base in December 2016. Likewise, Mixpanel's April 10 stats on active iPhone models report a 6.11% combined share for the iPhone 5 (3.77%) and 5c (2.34%).
Since Apple doesn't issue official data like this, these stats are the best we've got to work with. It's important to be transparent about this stuff in journalism's "fake news" era.