The ability to unlock the bootloader on most vendors has already degraded from "Do whatever you want!" to "Here, jump through these hoops here, give us all your data and wait a long time" to "What? No of course you can't do that!". Google can remove that functionality from Pixels at their first whim. I don't think this avenue will remain open for long. Smartphone hardware is powerful, but it's completely subservient to software that can't be removed or replaced.