This depends in large part on the discovery of new forms of energy. Modern cultures are very good at minimizing the effects of a problem. I think it'll be something of a minor inconvenience, as hydrogen power is optimised, or fusion power (Also hydrogen based, really.)
I think some people assume that scientists will solve their every problem so that they can just continue doing what they always have. It's a kind of blind faith that is a little disturbing to see. Science does not and cannot solve every problem, and it requires time and money to solve those problems.
If fusion power becomes a reality (and I am hopeful that it will) then the power needs of the world will be cared for. However, to get fusion onto the agenda it needs much more funding, much more support.
Societies also decline. For the past fifty years or so in the west, we have had it quite good. We don't remember the depression. We certainly don't remember the fall of any of the great civilizations. But history teaches us that despite science's relentless progress, society can also decay. We have to start planning now to avoid the worst. Greed is not good. Resources are limited and time is short. Research needs funding and support.
The industrial society is build on fossil fuels but as globalisation accelerates, rationalization advances and earth-population increases while the working population at least in high-developed-countries shrinks we have to acknowledge things won't go on as they used to. In order to slow down climate change we have to minimize the worldwide exhaust of carbon-dioxide. The global energy-needs could be completely provided by renewable energy sources. This should be mankinds main topic at present but it requires too much sacrifice by the wealth countries. If we don't change our way living on and treating this planet we will be erased by evolutions' next step.
"Peak Oil" doesn't mean the world will run out of oil, it means we will reach the "peak" of oil production, at which point we will start producing less and less.
If the world continues to use oil at current rates (I know this is not a reasonable assumption, but I'm trying to simplify things), most estimates indicate the supply of oil will last another 90 years. This is based on total conventional worldwide oil resources estimated at 2.25 trillion barrels. Some estimates put oil resources at more like 8 trillion barrels.
We will likely not reach this point anytime soon because the less oil that is left, the higher the price will be...which means that other energy sources (ethanol, nuclear, solar, wind, Canada's oil sands) will become more and more attractive.
The bottom line is, we have other energy sources, they just aren't attractive yet because oil is still so cheap. There may someday be an oil crisis, but there will certainly not be an energy crisis.
For more on all of this, just google "peak oil hype".
As time goes by power becomes more efficient. A gallon of gas today can take you much farther than it could years ago.
The same is true for all forms of power. So, the way the "haves" create shortages is by tacking a dollar amount on to the power.
The oil companies will "tell" you that solar is very expensive and therefor impractical and while they are doing this they are cooking perceptions in order to make that claim real.
Once solar gets concentrated and produces more milage in the same way that gas has done propelling automobiles will be no problem, the same as it is today except for the warping of the situation with the 'dollar bill".