Aside from urgency, it's also likely that wind, solar and hydro, even if deployed maximally, might not be able to meet the total peak demand every where. Renewable are obviously superior but for that gaps, we will need fission anyway.
Fission plants have a finite lifespan anyway so if fusion or space laser or whatever appear, openings will be appearing constantly.
Fission plants have a finite lifespan anyway so if fusion or space laser or whatever appear, openings will be appearing constantly.