That is what I thought at first as well. But if you go back to last year thread (assuming this year is similar to last year's process), someone was accepted from the waitlist the day right after the last interview. But yes, there is a chance we will not hear back until the week after. Also, from what I heard, adcom already know your admission status by the end of the day before they leave because they have a meeting right after. So it does make sense that they would start pulling people off the waitlist to fill up any remaining open spots. Realistically, most people will not hear back until May/June, if ever.
But what do I know, I've been wrong before. So......