I think it's a definite, not a probably. The universe is vast and there are going to be hundreds, if not hundreds of thousands of planets in the so called Goldilocks zones at a proximity to stars that can support life.
If you look at the way evolution has occurred on this planet (apologies to the creationists but I'm with Darwin, Richard Dawkins ftw), with convergent evolution taking place, there's a very good chance that species will have evolved in the same way on other plantets.
Of course there will be cases where evolution will have taken bizarre twists and turns there as well.
I have to say that if they did come here they've probably looked at the human race and thought we are the chavs of the universe.