There is a possible future where we mostly stop using oil for transportation, and then prices fall as supply exceeds demand. In the long term we'll eventually run out, but in the medium term, oil may become rather cheap.

If we continue to use transportation fuels made from oil, though, prices will likely remain high for the foreseeable future. There are likely to be weird fluctuations, though. (Remember when oil prices went negative a short time ago because there weren't enough containers to store it?)