Android P first developer preview has been officially available starting today. But the update is not available to its earlier devices, including the Huawei-made Nexus 6P, the LG-made Nexus 5X, and the Pixel C tablet.
While the Android P will be released on August or September, by the same time Nexus 6P and 5X will be three years old. So, Google is stopping its major Android update to its Nexus 6P and 5X as per its policy. But we hope it will release the security update till the end of 2018.