Lack of energy, the next "Black Death"?

I've recently read an article telling that after the Black Death (plague that impacts all Europe), the lack of available employees create social issues in sevral countries:
Workers asked for better working conditions and pay rises, fight to get it... and got it. The classic balance of power between employees and employers was modified.

In a world of mass unemployment where more and more things are automated, the balance power wont't evolve. Unemployment will stay strong.
Population will not decrease before several decades, except in case of WW3.

One thing can change the status quo: energy.

If energy cost a lot, humans will become again a good alternative to machines, local production a good alternative to outsourcing in China.

Perhaps we are living the last decades of the capitalism, because this system is fully based on nearly free energy.