idk what it even means to "solve" quantum gravity. Presumably it means to unify General Relativity with Quantum Mechanics. If it is solvable, what does that imply? That there's a particle for gravity? If the graviton exists, then what happens if we can stop it from interacting with its intended target? Does that mean something can be "shielded" from gravity? If so, welcome to insane propulsion. Probably not useful for moving people around a planet, but great for leaving the planet. Gravity is pulling me down. If I could "turn it off" for me, I'd shoot up at terminal velocity. The acceleration might kill me though, probably 0-60 in a nanosecond.

I'd say the gamechanger for humans will be the accelerating development of AI. Chances are AI will solve quantum gravity, not humans. And when that happens we'll be kind of overwhelmed by all the other crazy things happening, like an energy revolution, medical revolution, nanobots and macrobots doing work instead of humans, cities growing further into the sky, moonbases, Mars tourism, I'm probably going a bit far here but it's more fun to speculate about what AI can do for us than quantum gravity.