Considering that the universe has spanned (and will span) a quantity of both space and time (or space-time for those of you Astrophysicists out there) that completely dwarves how far and long life on this planet has existed and spread...considering the complexity of life and the odds...
It's almost certain. But as already mentioned I'm doubtful that we'll encounter other forms of life before humanity reaches its end and I'm equally sceptical that we'll recognise it as life when and if we see it. The concept that "Gods" from the past are actually other life forms makes sense but again, I have my doubts. Even if the odds were that other life couldn't possibly exist within logical reasoning, I refuse to believe that us and our planet are alone. That we should believe that humans are the only "intelligent" life in the universe (if we can even call ourselves that) smacks of ego and highlights us as special, which I disagree with.