That's just not going to happen by any measure. Deposits might become more and more expensive to tap into, but we're not just going to run out. We need to stop using them, not hope that we'll just stop once they are out - they simply won't be.
And even then, who knows whether dumping spare electricity into oil wells instead of e.g. batteries or pumped storage hydroelectricity might remain profitable.
My point is, it's not necessarily that obvious, and we better not wait for people to stop running out of ideas to make a profit on fossil fuels.