Sony has laid out the Android 8.0 Oreo upgrade roadmap for its Xperia line of smartphones. For the most part, Xperia device owners who have purchased a Sony smartphone in the past 12-14 months are in luck. However, there are some surprising omissions.
https://www.notebookcheck.net/Sony-confirms-Android-8-Oreo-upgrade-roadmap-with-some-surprising-omissions.246300.0.html
When talking about the Xperia Z series, you said Z3+ and Z4, when it is supposed to be Z3+ and Z5