The technological constraints and realities of space travel that will keep us bound to our solar system are often understated in our modern cultural hope of reaching for the stars. I've been guilty of this over here on my blog and in other writings although I find my own optimism in this area comes from an arena of hope, direction and a goal for the human species rather than on any certainty in technological progress.
Good article by Adam Frank exploring this idea over at the New York Times.
I agree (hope?) with the author that we will be able to successfully turn our abilities to the perhaps greater challenge of learning to productively and peacefully coexist with one another within the sphere of influence we will be able to reasonably create (the solar system). I can't help but feel though that we will still reach the stars in other meaningful ways such as through AI colonisation and/or remote contact with any other existing ETI civilisations already out there (and also constrained in spatial terms). And there is plenty of 'space' to colonise in virtual worlds here on Earth now and in the future.
Then again the possibility of AI, ETI and fully immersive virtual worlds are all currently open ended questions, so my position still remains ever hopeful in that regard...