I'm fairly sure Stevens will leave, since he's 88, but he's one of the liberals.  Kennedy is the only one that matters.  I've heard that he is thinking of retiring soon, although he's not very old by SCOTUS standards.  If Kennedy retires under Obama, that pretty much ensures that Roe lasts for another 20 years.

It would also mean pushing the Court to the left a bit on the death penalty and gay rights, although Kennedy has been fairly good on both.

Be nice to America. Or we'll bring democracy to your country.