Some day gas and crude oil will be a thing of the past. With innovations here and there. In your own opinion what will replace gas and crude oil in the international market.
I think most likely we will not have a replacement as crude oil and gas are not just what we use to produce fuel for various vehicles, but they go into many things. Mainly plastic, but also asphalt, solvents... And more.
So finding a replacement is very difficult as you would need to find replacements for many things. And judging by that, I do not think that gas and crude oil can be considered anytime soon a thing of the past.
Although personally, I wish it was. We are dirtying the ocean beyond imagination.