[redpoint5]

Right, and "better" alternatives could potentially replace fossil fuels (as fuels). We'd still have need of the many organic compounds, pharmaceuticals, and dense energy applications for things like flying. But if we replaced nearly all fossil fuel consumption in electricity generation and ground transportation, that would drastically reduce demand and drastically increase supply. Only the cheapest/easiest/best sources of fossil fuels would then be profitable in this scenario.

I'm not even saying this is likely, just saying it's possible. My hunch is fossil fuels will trend upward in unit price with demand remaining strong through this century. I'm not confident enough to gamble on it though.

Fusion is just one possibility. There's plenty of others, with just incremental improvements such as 4th gen fission, or improvements in PV or other renewable energy possibly disrupting fossil fuel consumption.

There's an upper limit to price for using fossil fuels as fuels too. If fossil fuels cost more than alternatives, then demand for them will drop. I'm sure there's a graph somewhere showing predicted demand at each price point.