Venus is too hot and that is likely the destiny of the Earth in a billion years as it gets closer to the Sun. However, one might be able to cool Venus and heat up Mars and with that knowledge regulate the temperature of the Earth. We have millions of years to figure this out.
The alternative of going to another star system seems even more unlikely than regulating the temperature of these planets near us, however, in a million years, I suspect we will know more about who is out there and perhaps make real contact with them. We may even pay them a visit.