A pretty good article.
However, I think you need to distinguish between the actual extractive industries (and properties such as fuel-in-the-ground) and the transport, storage, and distribution industries.
This means the entire infrastructure for transport, storage, and distribution of gas (methane) and liquid fuels, will arguably not become sunk costs, but will continue to be valuable for several decades beyond the end of fossil fuels.
I’ve discussed this in several articles, here for instance. It also goes into more detail regarding why we can expect the cost of solar power to continue dropping (roughly) exponentially.