I like when you said "replacing oil and gas is not as easy as some people think" oil and gas is still very important infact it's plays an important role in human existence since it's a mineral resource however instead of replacing it totally there would be alternatives for instance there's fiat and there's Bitcoin, Bitcoin won't completely replace fiat but would serve as an alternative, that's how it would be concerning oil and gas and other energy resources in the future. That's why not everyone is buying the idea of electric cars currently cause they still believe that petroleum powered vehicles are still very useful, maybe in the future their use case would be minimal but they won't be completely eliminated.
Is not as if I don't believe in advancement, it is good but we have heard about this replacement of a thing for a long time for a long time, I think what this means is that, it is actually not accomplishable although improvements will keep coming but running of engine without gas may not totally go into extinction, the only I see that will happen is scientists advancing to make a cleaner energy out of oil and gas, they have tried to shift grounds for other cleaner source but it's performance is what they are looking at, there is no way we will compare other source of energy to gas and oil.
The example your gave is correct, people have said many things about Bitcoin replacing fiat but it is funny because both has their functions and work together too, so I believe that's where you're making your argument from.