Yes and no. Yes I think it will protect independent processes sharing a computer that's fully patched. No it will not protect you if you run multiple untrusted

Yes and no. Yes I think it will protect independent processes sharing a computer that's fully patched. No it will not protect you if you run multiple untrusted scripts in the same process. This is partly why Chrome moved to isolate tabs in their own process after the V8 team eventually admitted defeat in implementing spectre mitigations.