It might not get us.. It shouldn't get Mars. Several simulations suggest it's 50/50 for the Earth.. But either way, life on Earth would be impossible. Mars will actually re-enter an age of warmth and liquid water during this time as well (temporarily of course).
Asteroids are a certainty. We're going to get hit. Many many times before the Sun is an issue. The potential for asteroid impacts are the number one reason for space colonization in my opinion.
I also think it'd be advantageous for humans to exist in multiple solar systems. This is obviously less important, but FTL travel would make finding Earth-like planets more advantageous (economically) than terraforming Mars or Venus.
And as ridiculous as it may sound, if any potentially hostile alien species showed up and decided to just kill everyone on Earth, well, it's not likely they'd stop there. They'd probably go after human colonies in the solar system as well. But if people existed elsewhere, in another star system, they'd likely have no idea where to find them.
By best estimates based on Kepler research, we estimate that there are 20 billion Earth-like habitable planets in the Milky Way. Assuming that the Milky Way is fairly average in size (it's not), and that there are roughly 100 billion galaxies just in our observable universe, then we can guesstimate that there could be around 2,000,000,000,000,000,000,000 Earth-like planets in our universe. When discussing planets that aren't Earth-like, that number goes up by several orders of magnitude.
Totally.. But I think we can be fairly certain we aren't alone in the universe.