I'm not convinced we will leave any fossil fuels unburnt without abolishing capitalism. Renewables will displace fossil fuel consumption more and more as prices drop and as compatible infrastructure is built, but as demand goes down the price of carbon fuels will also drop, when it gets low enough we'll of course start burning again. The industry has and will continue to plunge money into making extraction cheaper and demand for energy will likely continue to increase. It's hard to imagine energy ever being so cheap that it doesn't make sense, as in short term profit sense, to burn at least some fossil fuels. It's possible that we get close enough to net 0 that it's a rounding error but it seems at least equally plausible we end up at 30+ % of where we are now, if so all that carbon still ends up in the atmosphere within a century or two.