TL;DR (if you can’t be bothered reading all of the below) - Fosstodon will wait and see what happens, but if Facebook’s new service introduces any issues that could negatively impact our users, we will defederate.
More at https://hub.fosstodon.org/facebook-fosstodon-fedi
About the author
I'm a long-time user and enthusiast of open source software and espouse the philosophy that software code should be open (readable). So that everyone can see what happens behind the scenes while we use our electronic devices every day.