As it stands, I understand the research as eventually crude oil will run out. For the most part, afaik, our plastics are a useful byproduct of our oil consumption for fuel that would otherwise be more landfill waste. It's best to make reusable and long term use plastics from that material.

As to plastics from plant sources, it seems that a lot of what we do use for disposable containers and packaging are a better fit for those sources considering how well they break down. Of course, this all assumes that proper landfills are used and it isn't just shipped out of the country of use.