There are no 'waitlists' yet; only deferrals.
The letter essentially goes like this - starts off with the usual spiel on how they value your loyalty etc. and how there are only so many spots. However, because your application was good, they have deferred making a decision until 1 Feb 2011 though they can contact you anytime. If you am still interested in being considered, you should let them know and that they welcome additional materials to strengthen your candidacy.
So I wrote to them to still consider my application and that is when they wrote back to say 'cool, you have been released from the ED commitment' implying that I am now an RD applicant. So this is not a waitlist situation because being accepted in not contingent upon others dropping out; it depends on how my application compares with all the new applications coming in now in RD (though only till Feb 1).