Update - I decided to withdraw my application for Cornell STS because I accepted elsewhere. It sounded like the decisions will go down to the wire, so good luck to everyone.
I got a phone call from a professor there on Friday. He said they have already made all the offers they can, but that I was at or near the top of the list of people still being considered if some of the accepted students decline the offers. So I imagine anyone who hasn't been officially rejected is in a similar situation, but it does sound like a long shot since they only make around three offers, as ldh pointed out.
I applied but have not heard anything yet. Looks like since 2007 only two people have posted acceptances, so I guess we might not find much out until we hear from them directly. Also looks like in years past people heard earlier.