https://grapheneos.org/faq#roadmap

Apparently GrapheneOS wants to eventually become an independent OS with its own kernel, which would be awesome to see. I think RedoxOS and Genode are two other relevant projects so it would be interesting to see if they ever merge together in some way (which I also saw Genode had an aspiration of being a base for QubesOS eventually). Although for now it seems like they're not in a good state to replace Linux and Android, and it seems like QubesOS is struggling to catch up with modern technology.