I think the hope is that we bootstrap the renewable capable complex society on top of fossil fuels and then it can continue to function with the renewables it builds.
Then there's things like sand, water tables, synthetic fertilizers, and demographics to take into account too. You're essentially in a race against time to retool the entirety of society before the effects of fossil fuels either through climate change or human conflict destabilize the society past the point of being capable of doing so.
I would almost certainly bet against us.