We may never be able to make a viable colony off world. The moon is fairly pointless, Mars is hostile as hell, and our choices just get worse.
But sooner or later, we won't be able to stay here. We'll burn up too many resources. A pandemic we can't manage will come along. A larger proportion of the population decides science is evil, and technology is a physical manifestation of that. A big-freaking rock hits us. I dunno. But something will happen and all we are and all we have done will pass into dust. And the universe will go on, none-the-worse for our absence.
It's just, all I know, is that as horrible, small minded, hateful, and destructive as humanity is, we're also generous, creative, beautiful, and, as far as we can tell, unique in the universe. I think we're worth saving, some how.
I'm not saying that we're the only thing out here, I'm not saying we're better than any of a googleplex of theoretical aliens, I'm just saying we're the only thing in the universe we can know for damn sure is alive, aware, and capable of doing what we do, and damn it all, I think that's worth preserving.