Despite likely overstated "Saudi and friends" reserves, I'm fairly sure we aren't going to run out of the black stuff that quickly. It could get a lot more expensive because exploration and some of the new extraction processes are going to break bank, but running out is probably not the thing to worry about (However, know my bias, as petroleum exploration geology is
one of my back up plans if Navy doesn't work out...
).
And economical alternative energy production IS already happening via a whole slew of private solar, geothermal, nuclear, and tidal energy projects. Although I was talking more about the efficiency end of the equation with technologies that reduce your killowatt useage; green architecture, improved hybrids, and such.