Nuclear is the clear best option for a bridge technology. We already know how to do it, and there's a crap ton of fuel available in the earth's crust. With the proper effort, we could power the world with nothing but nukes.
But, even that will eventually fail. It may take many thousands of years, but fuel will run out. We should use nuclear power to keep society up and running while we move to solar-powered microwave transmission - solar collectors orbiting the sun at the Earth's Lagrangian points which beam the energy back to the surface in the form of microwaves. The technology is almost there; we just have to iron out a few details. And once we do that, it's basically free energy for a couple billion years.