Well, Joss specifically designed it so that humans were the only ones who inhabited the universe 500 years from now. Those are beliefs, that we humans are all there will ever be in the universe.
Which is why, in a way, i'm glad the series ended early...
you know by season 3 or 4 as story ideas begin to run out, the 'verse would eventually be invaded by hostile aliens, who would declare war on all of mankind, which would force all of humanity to unite against this common foe, thus ending the struggle between the browncoats & the government, and would ultimately prove to be the jump the shark moment of Firefly
...and i challenge SciFi to renew/revive Firefly for a few more seasons just to prove me wrong!!!!
