Twenty years from now, we will have searched many millions of exoplanets, only to find the same bland, racemic mixtures of simple compounds everywhere. The carbon/nucleotide-based life found on Earth (and possibly other planets/satellites in our Solar System) is the only such complex or directed chemistry in the observable universe. Aliens — specifically, any similarly continuous lineage of complex chemistry (broadly defined) that gathers, stores, and uses information, but is disconnected from our continuous lineage — dwell in their own universes, unobservable from ours. I believe that the experiments of quantum mechanics inevitably lead to this conclusion, and this is the resolution of the so-called Fermi paradox. The full argument is laid out at http://simplestcasescenario.com (free to read).
Challenge Karl Coryat to a bet on this prediction!