One way technology can really decrease consumption is by turning humans to machines. If you are essentially a CPU, your energy consumption would likely be very low yet your computational power and lifespan could be much higher. This way earth could support a much higher quantity of "humans", being mostly electric, it could even leave the confinements of earth, this way freeing earth.

The only challenge left is to maintain cognitive growth drives when you're based on electricity, rather than hormones among other chemicals.