[IWantToBelieve]

I remember reading a book on SETI. I can't fully remember the particular chain of logic/statistics presented in the argument for the case, but it goes something like...

Estimating that there are 100 billion stars in just this galaxy, and assuming that the universe is x billion years old, and that the creation of Earth and it's life forms took X+2 to 4 billion years, then the chance that there are sentient extra-terrestrial life forms of equal/greater technological achievement out there increases dramatically.

Also, conservatively estimating that 1/100,000 star systems support suitable planets for rearing life, then that would mean there could be another 10,000 sentient alien 'races' out there.

So given the math, I'd put money on it!