Well, the oil companies themselves have seen enough data to be certain.
Read a couple of Exxon's latest annual reports where they actually talk about it.
We can with a pretty good degree of certainty both know that oil will play out and when. The oil companies, who literally make it their business to know, and have hundreds of billions of dollars on the line have made their own projections and that lines up fairly squarely with a lot of the independently produced projections.
Oil production and extraction follows a very predictable, bell-shaped pattern. That pattern played out in each individual state in the US, for the US in the aggregate, and for every other major oil producing country. The same pattern shows up when one aggregates world oil production, or at least the first half of the bell curve has.
There is still a LOT of oil out there, but the oil that is there will require more energy and money to extract. It will be extracted as we progress down the downwards part of the bell curve, but simple physics will dictate that our demands for energy, all other things being equal, MUST go up as the efficiency of that source declines.
Please do not confuse the technological capacity to get at some oil deposits with being able to economically produce that oil, or, in the case of the massive amounts of sour crude, being able to economically turn that oil into a form where it's available energy can be used.
Here is a good bit on that:
http://www.abelard.org/briefings/ene...mics.asp#eroei
(quick note: oils actual EROI is currently estimated to be, according to that website about 30:1, but this varies widely depending on the source of the oil and its underlying quality)
You don't have to believe me specifically, but we are not finding new oil as fast as we are consuming it. The oil that is left will be less and less efficient in terms of the amount of usuable energy to be had from each new marginal unit.
In short, you are wrong about that. Oil WILL play out, and we are almost certain that it will play out at an increasingly fast rate over the next 40-60 years or so. There will still be oil pumped after that but not on any scale needed to sustain our economy in its present form.
Don't trust me. Do some digging, and some reading. The information is there, and readily accessible.