I wanted to take another stab at:
"I'm willing to pay more to fill my car with gas..."

First of all, if you willing to pay more to fill your car with gas, could say it's reasonable that future generations should also be willing to pay more?

Let me turn this around, suppose you could know somehow that future generations will pay less to fill their car with gas, would you then be less willing to pay more now?

I don't think it would be a bad thing if future generations paid more for energy, but I don't think they will.
Now, if people were to spend $20 per gallon gasoline in 2025, that wouldn't necessarily mean they are spending more money for gasoline- it would depend upon how much inflation there was over the next couple of decades. At 3% inflation $3 per gallon in a decade is $4 per gallon and in 2 decades is about $5.50, so if we had low inflation $20 per gallon would be expensive, but if we had inflation rates of Carter Era it would be around same price or cheaper.
Also another factor is relative purchasing power.
Gasoline prices adjusted for inflation:

Try again:

Purchasing power:

So, if you were living in the early 1980's and you were willing to pay more for gasoline, the next generation is actually paying less than you did. And I don't see why in next generation they couldn't be paying less than we are. But if they were to pay twice as much as we are at inflation adjusted dollars, but in meanwhile their purchasing power were to increase significantly it wouldn't matter much because the the fraction of the income could be less.

Now, just for fun, what will the internet look like in 20 years- are you guessing somewhat like today, or perhaps something which might be very different. What about China? I don't think it will match the US, but it probably make Japan fairly insignificant economically.

Now, I was looking around the internet to see what anyone had to say about global oil peak or energy peak. Not much has changed since last time I did this. But at wiki there was some interesting stuff. First I say as far as US proven reserves we have reserve life of 12 years and Canada has 182 year [at current rate of production]. Now it also claims that "The AEUB estimates that by 2016 Alberta oil sands production will triple to amount to 86% of the province's total oil production, and Alberta will by then be one of the largest oil producers in the world."
So, it's fairly easy guess that the US will be ever increasingly importing more oil from Canada.
And apparently Mexico has 10 years compared to our 12 years.
http://en.wikipedia.org/wiki/Oil_reserves

Another thing I found which I thought was interesting trivia:
"There are hundreds of coal fires burning around the world.[26] Those burning underground can be difficult to locate and many cannot be extinguished. Fires can cause the ground above to subside, their combustion gases are dangerous to life, and breaking out to the surface can initiate surface wildfires. Coal seams can be set on fire by spontaneous combustion or contact with a mine fire or surface fire. A grass fire in a coal area can set dozens of coal seams on fire.[27][28] Coal fires in China burn 109 million tonnes of coal a year, emitting 200 million tonnes of carbon dioxide. This amounts to 2-3% of the annual worldwide production of CO2 from fossil fuels, or as much as emitted from all of the cars and light trucks in the United States."
http://en.wikipedia.org/wiki/Coal

Just think if we could somehow put out those fires.