I'd answer the question if it made sense. It doesn't. You can't randomly choose a non-random sample, no matter if you "randomly" choose 100 from a general population, or 100 from a non-random subset.
What you really mean to ask is: Suppose you take a very large randomly chosen sample of people and administer an IQ test. How will the people that score 140 score on the second administration of the test. And I'll tell you EXACTLY how they'll score, as soon as I get a chance to do the math. Shall we agree on a mean of 100, and a standard deviation of 15, with a measurement error of mean 0 and standard deviation of...let's say 3?