I don't know if this is a joke, but I would not underestimate Wash U. Everything else aside, they have an assload of money and they are not afraid to use it. They have a larger endowment than SC, and almost half the students (i.e. better endowment:student ratio). If they keep spend, spend, spending, their medians can match USC-they're coming close as it is. And if Chicago hiring picks up, and the California market is slow to recover, I'd say it's borderline inevitable for them to tie or switch places in the next few years. It's conceivable, I tell you.
I can see Cal and UIUC dropping because of lower #'s. If that's the case, who better to take #21 than BU?