However, unconventional gas resources don't particularly play into this calculation. Gas (as in methane) is a completely different resource in this context. The markets are different and the reserves are very different (there's a lot more methane). The "peak oil" debate focuses on liquid hydrocarbons.

There are several liquids-rich unconventional "fracking" plays (e.g. the Bakken in North Dakota), but they're not particularly common. Oil shale is a much bigger player in terms of volume, but again, you're looking at slow, expensive, environmentally costly production.

It's certainly more of a long-term problem, but it is something to be worried about. It's hard to replace liquid fossil fuels in terms of energy-density per unit volume. It's a problem that we as a society need to be working a _lot_ more on.

That seems like a bizarre thing to believe. When humanity switched from wood to coal for heating, or from coal to oil, were either of those an identifiable "historical event"? If we switch from oil to other fuels in our lifetimes, this will happen so gradually that nobody will notice when it happens. Any more than we noticed as "an interesting historical event" the moment that everybody got an email address, or started using google, or bought a smartphone.