i think rudisha is a 10.7-10.5 guy flying. doing this off the blocks is a whole different ballgame. in the 2 or 3 400m's i've seen rudisha run, his starts looked nowhere near 11.0, but the others in the race probably were.
i also agree that many 47 high runners can run sub-11. the question is, can they run a decent 800 without doing a +8s split?