I understand from GrapheneOS' socials they are working on the Android 16 port, however due to conscription and not having the full trees it's more difficult than usual.
The concern is how this will affect the project moving forwards. Will GrapheneOS still be able to promise and provide its usual level of security assertions, or are there compromises as a result of the increased difficulty - especially when having to 'reverse engineer' parts of the code.
Clearly this is - and it feels like - an attempt to push users off custom roms and GOS by ensuring they expend what little resources they have. The more difficult porting becomes, the harder it is to provide timely updates, the less interest there will be overall. There has been a consistent and systemic attack on custom ROMs with things like Play Integrity and so on, which on their socials GOS has already complained about, heavily.
Realistically, even if Android 16 hits soon, I would expect these changes to cause the developers to lose interest in a losing-battle scenario where it becomes too difficult to maintain this project in the long term.
This is just the next but crucial step in Google asserting control over Android entirely.
The difficulty being that going back to stock Android or even iOS is a major threat to online security/privacy, which is why we are all here anyway; not being able to block apps access to the network, or the significant hardening which Graphene has contributed to in the kernel (and even upstreamed their changes to the betterment of all). For many it's a compromise that is not acceptable, however with smartphones in some cases almost being 'mandated', even if GrapheneOS just stops development, they will be forced into Google's sandbox, which is a feature, not a bug.
I do wish the developers well, and hope this project is alive and well in the next 5-10 years. I have my doubts, but hopefully this is an obstacle that incentivizes them to continue rather than quit and give up entirely.