And people have been looking at the exhaustion of fossil fuels since the late 18th century. Yes, 18th, not 19th, with the first questions arising over how long Britain's coal would last.
In that time, the three big developments have been accessing petroleum (1859), commercial electricity generation (1870s), and nuclear fission (1935).
Petroleum replaced one fossil fuel with another (albeit a vastly more useful one). Electricity allowed for energy generation and use to be decoupled by thousands of miles, if necessary (transmission losses for long-distance electricity are quite low). And nuclear fission offered one possible out, though it's been a highly problematic option.
Wind and water power have been utilized by humans for centuries, if not longer. Solar power has progressed hugely in recent decades, but it's far more fundamentally limited than many people realize. Raw availability at Earth's surface is ~8,000x present human energy consumption. Factor in land area (30% of total), population and per-capita energy growth (roughly doubling energy demand even at a small fraction of present US energy use levels), total conversion efficiencies (you're left with about 1% of the available incident energy after PV conversion, capacity factor, spacing factors, and inverters), and we're down to a 20x surplus of solar energy as available capacity if you pave over the entire Earth's landmass.
You start rapidly arriving at the conclusion that either we're 1) not going to see levels of resource consumption comparable to those of the advanced world, or 2) not for projected populations, or both.
You can hypothesize alternatives, but most are assuming tremendous advances which have been exceptionally non-forthcoming.