It's clear that this rate of growth is not sustainable. Everyone knows that, though not everyone acknowledges it. Population growth must top out somewhere. The most likely mechanism is the same one that's driven birth rate decline in developed nations: affluence. The end of huge scale population growth doesn't mean human extinction or even significant population decline, though it may mean financial crisis and a major re-invention of modern finance around models that do not depend on eternal massive GDP growth.

Wars of course will happen. People fight wars. Modern wars don't have body counts like they used to. A war between the USA and Russia or the USA and China would -- unless nukes come out in force -- be largely fought by machines with body counts far lower than WWI and WWII. (USxChina would be a full-on cyberpunk mech battle.) Wars also tend to be followed by periods of expansion, so don't pin your "hope" on war to reduce human population or environmental effects in the long term.

I've simply come to terms with the fact that we have entered the Anthropocene. The holocene geological epoch has ended.

If you want to slap a date on the anthropocene, I'd go with July 16th, 1945, the date of the Trinity atomic test. That was the point at which the evolutionary ratchet clicked and regression to a pre-industrial state became game-theoretically impossible. Subsequent atomic testing also furnishes a nice neat line in geological strata that will be clearly visible to any geologists of the far distant future.

We are in the early anthropocene, which seems characterized by increased CO2 and methane concentrations, increased temperatures, and plummeting biodiversity. The latter is a common characteristic of geological boundary events. The fact that this one was caused by the emergence of large scale industrialized intelligence instead of a meteorite or volcanism doesn't much matter. When the environment drastically changes a lot of species die off.

What happens next is debatable. It's likely that intelligence will soon figure out massively scalable renewable energy (it's close) and/or fusion. That combined with depletion of fossil fuels will mean CO2 emissions will probably fall off a cliff by mid-century. The big CO2 pump is probably a H-A (Holocene-Anthropocene) boundary event like the line of radioisotopes from early atomic testing. CO2 has a long half-life in the atmosphere but we don't know what biology is going to do as the planet warms and all that CO2 is hanging around. There could be a huge burst in photosynthesis. The Cretaceous period, the last epoch with similarly high CO2 concentrations, also had about 150% today's oxygen concentration in the atmosphere. Maybe that will happen by a few hundred years from now. I'm thinking the Anthropocene is going to look a bit like the Cretaceous.

The loss of biodiversity here on Earth is depressing, but on the positive side it's likely that the Anthropocene will see the spread of organic life from Earth to its Moon, Mars, and possibly other locations in the solar system. It may also see the birth of self-replicating machine intelligences, an entirely new offshoot of life adapted for large-scale growth beyond the planet's biosphere. A moderate number of humans and associated symbiotic plants and animals might colonize other worlds, but I'd predict that post-biological life will make the big leap from atmosphere to space (analogous to the leap from the oceans to land). Us with our clunky space suits are like lungfish.