Energy is still limited. At our long-term growth rate of energy use, we have fewer than 300 years before we start observing warming from thermodynamic limits on energy dissipation[1]. This is completely independent of the method of energy production, and simply a function of how quickly the Earth is capable of radiating thermal energy out into space.

[1]: http://physics.ucsd.edu/do-the-math/2011/07/galactic-scale-e...