There isn't going to be an unbounded exponential growth, and every techno-prophet knows it (as opposed to armchair economists) - if we keep basing our economy on endless growth, everything will go to hell when we hit the natural limits.
Be creative: unbounded exponential growth would mean, for instance, that at some point in the future the global yearly energy consumption would be higher than what E=mc^2 suggests for m=mass of the earth.