Vaultwarden (and all the client apps) depend on Bitwarden for the API spec. If Bitwarden introduces closed features in the API that Vaultwarden can't/won't implement, but the client apps do, it will split the spec. They can also introduce API license keys, which would render Vaultwarden mostly irrelevant.
The only way for Vaultwarden to remain relevant going forward is to own it and split ways from Bitwarden. This would in turn mean that the FOSS client apps have to decide which to support. But I think the ecosystem is going to fragment eventually anyway, so the sooner every app decides which way they want to go, the better.