To be a good kernel. One imagines that, insomuch as a good kernel is part of an OS, that it could 'replace' Android and Chrome OS. But the days of platforms getting sunset are a day of the past, the Android runtime survives and will survive for years.
Maybe. I think they’ll continue rolling it out to simple devices for a few years while they do extensive testing and fix any issues that arise but I do believe their long term goal is for it to be a replacement for all their various Linux based OSs (since it is supposed to be able to run on simple devices all the way up to smart phones and PCs.