The current global economy is based on oil.
That is a limited resource. Doesn't matter if you believe we have a 10 year supply, or a 1000 year supply - it remains limited and is being consumed at a rate that is unsustainable.
Personally I think we are going to see a major shortage in the next 15-25 years, but that is just opinion. Its based on the current cost of extracting oil, in terms of energy usage, vs. the quantity of energy extracted in the form of oil. In rough numbers, in the 1950s it cost 1 barrel of oil to pump something like 50 barrels out of the ground. Today's fracking technology cost 1 barrel of oil (you didn't think heating and pumping was free did you?) to pump something like 4 barrels out of the ground. Basically, we have pumped all the easy stuff.
Fortunately, renewables are finally starting to make an impact, and its easy to predict a day when most vehicles will be electric powered.
Unfortunately, cheap oil going away will shutdown the current airline industry, and serious impact transcontinental and ocean based shipping.
In a way, this will be a good thing for us long term: More local food supplies and locally produced products - but less choice and say good-bye to Oranges in February in the mid-west USA.