I'm not at all convinced that AIs will inevitably expand at near-light speed, but if they do, then it is still surprising that they haven't encountered us. This is of course just the Fermi paradox, but still provides some evidence that we might just be very lucky and at the beginning of the pack.
If AI's don't necessarily expand much, then our outlook is even better, and concentrating on FAI here on Earth is especially important.
Lastly, it might be unlikely, but it seems possible that a young FAI on Earth could protect us from an older UFAI.
Why do we imagine our actions could have consequences for more than a few million years into the future?
Unless what we believe about evolution is wrong, or UFAI is unlikely, or we are very very lucky, we should assume there are already a large number of unfriendly AIs in the universe, and probably in our galaxy; and that they will assimilate us within a few million years.
Therefore, justifications for harming people on Earth today in the name of protecting the entire universe over all time from UFAI in the future, like this one, should not be done. Our default assumption should be that the offspring of Earth will at best have a short happy life.
ADDED: If you observe, as many have, that Earth has not yet been assimilated, you can draw one of these conclusions:
Surely, for a Bayesian, the more reasonable conclusion is number 2! Conclusion 1 has priors we can estimate numerically. Conclusion 2 has priors we know very little about.
To say, "I am so confident in my beliefs about what a superintelligent AI will do, that I consider it more likely that I live on an astronomically lucky planet, than that those beliefs are wrong", is something I might come up with if asked to draw a caricature of irrationality.