Given the many random chances that seem to be necessary for sentient life to develop -- a star that's not too hot or too cold, small enough to be stable for long periods, far enough from galactic center that its planets aren't regularly sterilized by radiation from supernovae and gamma ray bursts, that has enough heavy elements to form metal-rich planets, has other, larger planets to sweep up "debris" left over from the system formation, has a planet that's not too close to or too far from the star, too large or too small, with a relatively large moon to stabilize its rotation and catch even more of the cosmic "debris" -- I think intelligent life is going to be very, very rare.

So there may be others out there. But they are simply so far away, we'll never even know they're there.

Edit: Heh. Got caught up in the writing and forgot to say that I also agree that our only hope for long-term survival is to get out of this system completely. And the benefits of just trying would far outweigh the costs.