I am currently at MIT and trying to switch to TPP and had to apply. Up to last week I was informed that the admission committee was still making decisions. Not everybody is invited to the open house so you may receive your admission notification after the 14th. When I applied to my current program last year I got my admission letter the week before the open house so it's not too late.MIT tries to send out notifications after other schools so that you can fully evaluate all your options. In addition, spots may open up later on as some people defer or turn down offers. So unless you get a rejection letter before March 31st you still have a chance of being admitted.
Good luck!
