Apple’s official App Store measurements put iOS 10 adoption at 54%.
Mixpanel’s version of iOS 10 adoption is, obviously, not measured by App Store internals. According to the latest Mixpanel trend numbers, the iOS 10 adoption rate is 67.21%.
Both sets of numbers are reasonably up to date and, also obviously, pulled from different sources. Apple pulls data from App Store visits on a specific day (in this case, October 7th), and Mixpanel pulls their data from web site visits, sort of like Google Analytics, though with a deeper embedding in applications.
Interesting to see such different measures of adoption. Regardless, iOS 10 has a significantly higher adoption rate than Android Marshmallow (about 20%). As a reminder, Android Nougat is the latest and greatest, but it is limited to a few devices at this point, so Marshmallow owns the largest slice of the Android pie.