Personally, I think that in our own galaxy alone, there are tens of thousands of life-abundant worlds, with approximatly 1000 of them nurturing 1 to 5 native intelligent races each. The chances of some being within 20 lightyears of Earth is something I cannot answer, but I would imagine that there would be no more than 50 space-faring races technologically capable of spanning the galaxy, based on the risks and difficulties of space travel. Now, those 1000 worlds with intelligent life do not include worlds colonized by space-faring species, nor do they include all the extinct races or any of the other 100 billion galaxies that we know of (key words: that we know of).



The Drake Equation is very ingenious, if you ask me. However, like you said, it does not include any of the extra-galactic races. Not to mention, as of right now, there is no way we can determine just what 'N' stands for. Until we become a space-faring race ourselves, we can only speculate. Besides, in my opinion, actually travelling through space and encountering the aliens in person is the only sure way of answering that question.