It won't take a long time for alternative energy to become prominent since most of the techniques have already been around for decades, it's just a question of making them more feasible economically. I reckon by 2030/2040, most developed countries will have become more self-sufficient in energy production reducing fossil-fuel consumption drastically
not only is oil/gas critical now, but there are no viable replacements in our lifetime. people who think renewables can replace oil within few decades are simply ignorant of how big oil really is. there is no reason whatsoever to think any feasible amount of renewables growth can displace fossil fuels in a couple generations. wind and solar are growing exponentially, yes, but from such a small base that it doesn’t even make a dent (i have all the stats)
sorry buddy, but regular old exponential growth isn’t even enough to match oil, you’ll need half a century or more of clear energy superiority. that means cleaner and cheaper and more concentrated for storage. as of now, nothing fits the bill yet. to replace oil, you’ll need a century to allow the entire economy to retool and realign around the new technology and dispose over a century old industry; that is unthinkable feet
not to mention the amount of wealth that is generated from.. entirely another chapter of discussion itself
