Firefox is essentially owned and paid for by Google. They already have their own manifest 3 in the works. They will ultimately do whatever Google wants.
Most of the forks are poorly supported. Remember that the Pale Moon archive was actually infected with a trojan? That sort of thing doesn't happen at big companies that have someone in charge of verifying security.
@number6@bremner Firefox will support manifest 3, but has no plans to abandon manifest 2.
Mozilla is desperately trying to get other sources of income than Google paying to be the default search engine. This is why Mozilla VPN and Firefox Relay exist. Buying them supports Firefox development.