I also think that we underestimate the amount of unused resources that we haven't tapped into yet (e.g. planets in our solar systems) and the resources that we might not even know about yet (e.g. new forms of matter or "new" laws of physics). Also, it seems likely that paradigm-shifting technological breakthroughs will continue pushing the boundaries of our growth further out. An interesting read in that respect is "Thinking in Systems" by Donella Meadows. In the 60s and 70s, the systems thinking approach outlined in the book also predicted that our planet would soon hit it's "carrying capacity" and further growth would be stunted. A major reason this didn't happen was (IMHO) the rate of technological change, which moved the carrying capacity of the planet well beyond what would've been possible 30 years ago. The same processes that were at work then are still at work today and constantly change the technological background against which we make our assertions, which makes systemic estimates of macro-economic systems a very tricky business.
As they say, the stone age didn't end because of the lack of stones ;)
Starting with 7.4 billion people in 2016 and a population growth rate of 1 % per year we will reach the carrying capacity of Earth in less than 1400 years - the body heat alone will raise the surface temperature above the boiling point of water.
Once we reach the carrying capacity of Earth - no matter when that is - and decide to move into space we have 2685 more years until we run out of places to live in the Milky Way assuming 400 billion stars and one Earth-like colonizable planet per star.
Unfortunately 2685 years is not nearly enough time to reach all the stars in the Milky Way even if you would be traveling at the speed of light, you could cross just about 2 % in that time.
There are very real limits to the possible growth and we are talking about centuries or a few millennia. With a growth rate of 0.1 % per year one can push that to tens of millennia but that is still the blink of an eye in the grand scheme of things. And while I used population growth, things of course don't change if you substitute energy consumption per capita.
It is very unlikely the population of earth will continue to grow at 1%. In the best scenario, we will have worldwide development followed by a fall in fertility that it inevitably brings. In the more morbid ones, climate change, wars etc. will result in a large amount of the population getting destroyed.
As they say, the stone age didn't end because of the lack of stones ;)