The world would get on pretty well even with 7 billion people if we left large uninterrupted areas of wilderness unmolested, produced our crops with hydroponics, priced the most land/water-intensive foods out of mass availability, took a harder stance against disrupting keystone species, and ran on renewable energy.
All of those are possible, but depend on international government measures that have varying likelihoods of ever happening.
The world will definitely be transitioning to renewables over the next century, we should reach a majority of it in the first world over the next decade or two. That's the easy part, because we're reaching a point where renewables are at cost parity with other forms of power. The other aspects are much trickier, being more disruptive, with requirements and mindset problems that we've barely begun to tackle.
