If he keeps it up at this pace, he'll earn his blue belt in October, be a red stripe before Christmas, and earn his red belt just after his birthday. Once he's a red belt he gets to start breaking boards. After red belt he has to earn 3 black stripes before he gets his black belt. So, as long as nothing derails him, he'll get his black belt sometime when he's eight.
I can't tell you how proud of him I am.