Matrix is an open, federated protocol so something like this can't happen. Worst that could happen is bad stuff happens to Element (the flagship client) at which point people can either fork it or simply use another client.
This assumes that there’s enough volunteer capacity to maintain it and that federation remains open despite business incentives to close it or the maintenance costs (i.e. spam).
That could be true but the track record hasn’t been good and it definitely won’t happen without a concerted effort to support it.
I think there is a big enough community to maintain it, should that ever happen. There are multiple totally community-made clients that work well, and there's at least one community-made server that's getting close-ish to federation, even if no-one forked Element/Synapse/Dendrite.
