Blacksky has already built their own ATProto stack that's fully independent from Bluesky.
Now Eurosky is making progress as they roll out their own PDS.
I see more independent infrastructure springing up on https://atp.fyi/network, including AppViews.
For anyone hoping that we'll get another wave of people coming to the fediverse once Bluesky folds/enshittifies, that might not necessarily be the case as people will have more options to stay in the Atmosphere.