There's still the big question mark of "will it be economically viable?" By the time Fusion is ready we might be heavily transitioning to cheaper renewable energy sources and not want to subsidize expensive power.
Very good point. Doubtless though, if it ever achieves technical viability, fusion will have a niche, because not all applications require economic viability. Can't beat the energy density it provides, either. Would be great for outer solar system missions.