If not voluntary, then forced. The ecosystem that carries all the growth is rapidly falling apart (relatively, with speed measured in decennia, generations or centuries). We cannot stay on the exponential paths we've taken the last 250 years for another 250 years, that is impossible. Let alone for another 2500 years
Just population growth alone, using the current curve (1.1%), will hit 118 billion people in 250 years and 5,812,724,005,588 billion (not a typo) people in 2500 years. Compounding exponential growth is quite literally unimanigable.
We cannot continue on current curves. No matter how efficient you make houses, produce iPads or food: exponential growth is unsustainable. Literally and figuratively.
There are a couple of different population projections out there and, of course, predictions about the future are hard. But all of them show a population peak around 2100 of maybe 10-12 billion people.
The same holds for population growth. As countries get richer the birth rate reduces. So there's very little chance that we'll stay on the current 1.1% curve, any more than we stayed on the analogous curve defined in 1950.
I would guess that the marginal value of cleverness or technology decreases over time
On a note addressing your population growth numbers, I just want to say that your numbers demonstrate that you are very unfamiliar with population growth dynamics and you should research the topic more. Those numbers are impossible and not going to happen (on earth) in any scenario whatsoever.
Agreed. Collapse or increasing eco-terrorism is my guess.