The Kepler-spacecraft team recently released this extrapolation from their spacecraft’s results. That spacecraft looks continuously at the stars in an area about 0.4% of the sky, an area roughly between Lyra and Cygnus. Planets passing between their stars and us will make the stars’ light go down a little bit, though one has to be careful to distinguish between that and various other sorts of variability. It would also be good to try to observe some of these stars with other telescopes and instruments, to see if Kepler’s observations can be repeated.
But after observing about 150,000 stars, the spacecraft has found evidence of over 1000 planets, with over 50 in their stars’ habitable range of distances, not too cold and not too hot for liquid water. Since that spacecraft can only see evidence of planets whose orbits are nearly edge-on to us, that means that at least 1 in 2 stars in our Galaxy has a planet, and likely several planets.
I find it very satisfying to see a great dream come true in my lifetime. I had not expected to ever see much evidence of planets of other stars, but here it is.