Chances are that there IS only one, or at most, a few different types of possible "life" out there.
I would ask 'why?'. This is similar to the phrase 'planets capable of supporting life' which is a major pet hate of mine. I think we need to discover at least one form of extraterrestrial life before we can start making claims of what life is or isn't capable of in the universe.
Don't get me wrong, you may be right, but I personally don't think we can start making statements, claims or predictions until we have a little more information to base our analysis on.
I do wonder though what makes you think the 'chances are' that way? I would say that in a universe as big as ours, anything is possible.

