even though the are tons of people coming online everyday, will it eventually get to the point where 4 letter domain would have to become scarce like telephone numbers have become. if so, at what rate could something like this be calculated?
People already tried that. There were hardly any 4 letter .com names available by Year 2000. Now, many (including some that I own) are being forfeited. Do not buy just because it has 4 letters.