Re USC - I emailed one of the faculty I had been in touch with. There had been a weird glitch with their system so when I didn't hear back I was worried it was because of that. He was super nice about it - but alas, no acceptance. Also, later that day I spoke with a friend who interviewed with USC and though he hadn't heard back, someone he knew had already been accepted into the program. Perhaps they wait to know who will accept before doing final notifications?
I imagine that is what is going on with Irvine and RISD - but I am ready to start making a decision, so finality would be nice.