We didn't know what electricity was 300 years ago. And the best way to get around was riding on the backs of other animals.

We're maybe 70 years away from being a multi planet species if technology keeps advancing at the same rate.

We just need better ways to get into space. If the Sabre program works out or we figure out fusion power we'll be ready to roll in 20.

Or we could figure out self replicating robots. Nature has been doing it a billion years so we already know it's possible.

Or, just create a robot species in our image to explore for us. And hope they keep their meaty parents around and happy

There's multiple paths for humans to get off the planet. Out of the solar system, maybe not. But it's damn hard to predict farther than 100 years into the future