If you look at the nuclear binding energy curve (e.g. https://en.wikipedia.org/wiki/Nuclear_binding_energy#/media/... ) you'll see a nice bump there for He4. So there's no gain in fusing heavier stuff.
So that's at least 20 years away from being 20 years away from being 20 years away. And you could just make more alpha particles, anyway. It's not like the universe is short on hydrogen.