The kepler telescope, not content with beating the crap out fo astrophysicists theories about how planets are formed, just keeps pumping out new planets. Or discovering them rather. So we've discovered earth sized planets, we've discovered gas giants and even some planets smaller than earth. Most of the earth sized/rocky ones aren't in the habitable zone, some of the gas giants are, but that doesn't really help us. What happens though, when we find a rocky, earth sized planet in the sweet spot of the habitable zone of a sun-like star? At the rate Kepler is going, it's got to happen sometime. I can't find the link at the moment but there are physicists who are measuring the atmospheric composition of exo-planets - when we find it we can even see if it has water/oxygen/nitrogen etc. Are we going to get off our collective arses, get our shit together and actually try and get there?
update: And then Kepler really puts the boot in.