Well, in about 500 million years, the moon and earth will be closer to the sun than Mercury is now, as it expands into a red star. So we probably need to start working on moving - maybe to one of the moons of Jupiter. Use the moon to launch to Mars, then from Mars to Jupiter.
The red giant phase won’t happen that soon. There’s still about 4 billion years to go before that. That said, in about a billion years the Sun will be about 10% more luminous than it is now as it burns more hydrogen and the Earth will be unlivable anyway.