If Android is to be forcibly split from Google due to legal decisions then there is a risk of the new organisation being even more hostile towards this work. They may not even choose to keep it open source, in a worst case.

Even if a fork happens to continue where left off, there could be security shortcomings, the new team may not be committed to security at all. Where to rebase would need to be a heavily thought out decision.

Google provide financial incentive by paying security researchers to uncover vulnerabilities in Android:

https://bughunters.google.com/about/rules/android-friends/6171833274204160/android-and-google-devices-security-reward-program-rules

Id personally be unsure if such incentives could even be continued. If there's no reward, some people won't do it.