Unless we find a way to 'produce' (the P in GDP) without increasing entropy by digging up stuff (oil, metals, whatever) and then releasing them into our ecosystem once we're done with them, those limits seem to be pretty close though.
That's not just me thinking that. That's the Club of Rome, in the 70's.
As long as the Sun shines on (and this is essenty “for ever”), there is an increasing accumulation of energy in the planet: that is where the possibility of exponential “growth” comes.
Your point is invalid because it would require an exponential growth of the sun power (the derivative of an exponential is an exponential). While the sun power is exponential around a billion years, it is a constant over a year. So you would reach at most a linear GDP growth.
Not so fast. Entropy is decreasing. There might be more energy, but useless energy. Energy low enough, spread out enough or with too little temperature differential that you can't do much or anything with it.
The Earth is getting solar energy sure. But it also emits energy. And a lot of what stays here is just useless heat.
That's not just me thinking that. That's the Club of Rome, in the 70's.
https://en.wikipedia.org/wiki/The_Limits_to_Growth
Their conclusion at the time:
"the most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity"