There has been a lot of press today covering Android P and the first developer preview dropping. That is certainly news worthy because, honestly, it came a week or two earlier than expected. But what is not news is the fact that the Nexus 5X, Nexus 6P and Pixel C tablet will not be getting Android P, officially at least. Google has made it very clear and very public when support for these devices would end, both in major releases and security updates.
While we can debate all day long if two years of software support is too short, it is the number that Google settled on and has published for support of devices. The only exception, and likely the way going forward, is the Pixel 2 lineup which gets three years of major updates. For the Nexus 5X and 6P, major build support ended in September 2017. That means Android Oreo was the last major build.