I think the future market for refined petroleum will be increasingly limited, over time, it's tough to project when that really starts to reduce usage. Economic growth will counter that for a while of course. By 2050, it's reasonable to think over half of cars and LTs will be powered by something other than gasoline. So, perhaps the market will be something close to half what it is now, maybe. Then we have usage by other means of transportation that may not evolve as quickly. And then there is the use in making chemicals and plastic etc. (which is pretty substantial). If you start a new refinery now, it is going to take ~3 years to be operational. I think we'll see more expansions rather than green field operations. Oil companies no doubt have looked hard at all this and have better projections than I do.
At some point, the market for oil is going to be much lower than it is today.