I am waiting as well butI am not sure about the "waitlist" thing. Because based past few years records, there should be much more posted rejections from MIT Mechanical. I think this year is just they slowed down the process and many people are on that "waitlist".
Cornell released some decision on 2/4 and it's all acceptance!! Based on past searching results,they release all the PhD acceptance during early of February and then all rejection in the mid March! I am so depressed and having a panic attack.