Rene Ritchie shared a comparison of iOS adoption rates over the years (starting with iOS 7 in January 2014) and, so far, iOS 11 has the lowest adoption of all major updates, four months after their public release.
iOS 11 as of Jan 18. 2018: 65%
iOS 10 as of Jan 6, 2017: 76%
iOS 9 as of Jan 27. 2016: 76%
iOS 8 as of Jan 7, 2015: 68%
iOS 7 as of Jan 27, 2014: 80% https://t.co/gGh1U8vvLb
— Rene Ritchie (@reneritchie) January 19, 2018
Looking at the numbers, you can see a decline in the transition from iOS 7 to 8 (iOS 7's troubled rollout affected millions of users for months), a stabilization with iOS 9 and iOS 10, and another decrease with iOS 11 this year.
I see two potential reasons for this. With iOS 11's 32-bit cut-off, it's very likely that a good percentage of users who would have updated simply couldn't because they were on older hardware not supported by iOS 11. More importantly though, the widespread perception that software updates make Apple devices slower isn't helping adoption rates. This time, Apple itself had to confirm that iOS 11 did, in fact, throttle iPhone performance to compensate for aging batteries (a perfectly fine motivation, terribly communicated to customers from a software design and PR perspective).
A couple of weeks ago in our 2018 Apple predictions episode on Connected, I mentioned that I believe iOS 12 will have a focus on speed and performance as a tentpole feature, specifically called out at WWDC as an important effort by Apple's engineering teams. This is just my personal theory, but I don't think new emoji and Animoji will be enough to convince reluctant users to update their iPhones later this year. If Apple wants to counter the narrative surrounding iOS 11 and see these adoption rates pick up again, I think they'll have to demonstrate – not merely promise – that their next software update will have practical, tangible benefits on the everyday usage of an iOS device.