"I think it is likely (20% or greater) we will compete for resources against non-terrestrial lifeforms before humans leave the solar system, assuming we leave the solar system."
If you want to believe that, fine, but be aware you're believing despite a complete lack of evidence. There's little more than a faint trace of a sign of any life in the rest of the solar system (a few stray whiffs of methane on Mars that aren't that hard to explain geologically), and absolutely no sign of any sort of life that would provide any sort of competition if we decided we wanted their resources.
I don't mean that it would be a fair competition. I meant competition in the same way we compete for fresh water with plants. If there isn't enough to go around we always drink first. My 20% is entirely based on what I think the odds are that single cell microbes exist, possibly in a dormant state, somewhere near a water or methane source in our solar system.
If you want to believe that, fine, but be aware you're believing despite a complete lack of evidence. There's little more than a faint trace of a sign of any life in the rest of the solar system (a few stray whiffs of methane on Mars that aren't that hard to explain geologically), and absolutely no sign of any sort of life that would provide any sort of competition if we decided we wanted their resources.