I think it's very possible that other intelligent life has developed somewhere else in the universe in almost 14 billion years. After all, it happened here. However, I don't think it's a stretch to say we are alone, or that we'll never encounter another intelligent life form. There are just too many conditions required to occur simultaneously for life to develop, and even more for life to continue existence long enough to develop intelligence before being wiped out by natural or unnatural causes.
Remember that life didn't appear here until the universe was already 8 billion years old, and what we consider intelligent life didn't occur until roughly 300,000 years ago. Technologically advanced intelligence capable of recognizing a small portion of how the universe works came only within the past minute sliver of Earth's existence. If you believe the available evidence, the universe has been expanding at great speed since it was created so that by the time life appeared on earth we would have been vast distances away from another such body where it might have appeared in a relatively similar time. If that were the case, how would we know of its existence? Even if our technology reached a point where we could detect its existence and somehow determine some evidence of intelligent life there, that evidence would have been present billions of years before its discovery, since that's how long it would have taken for the evidence to reach us to be detected. In that time, the life form could easily have vanished, so expecting that its existence and ours is concurrent is a stretch too remote for me to accept.
I'm not saying that such a meeting of two coexisting intelligent life forms is impossible. What I am saying is that the meeting of humans and another alien intelligent species exists in the improbable, if not the impossible.
