Good point... apparently not. It's supposed to be very close though.
http://www.joystiq.com/2013/12/22/he...pt-in-still-a/
You should opt-in tonight. Not sure if that Jan 7 date is still accurate, but if it is, then your last chance to get into closed beta is opting in by then. At one point last month they said they invited everyone that opted in, so they've been pretty liberal with the invites.