Let k(n) denote the minimum number of iterations deeded to make sure that every polygon with n side becomes convex after at most n midpoint iterations.
It is clear that:
Further, it is not hard to see that
which we may check as follows:
To get an idea as to what is the probablity that a random 4-gon is convex:
So this seems to suggest that a random 4-gon is convex about 30% of the time.