The transcript of the Davenport Supreme Court hearing yesterday is available here. From a quick read through, things don't look good for the unions.
A large majority, even 9-0 against the unions is likely, but one opinion does not seem likely. I would say that Chief Justice Roberts, Justices Kennedy, Scalia, Thomas, Alito and probably Souter will be on the main opinion. I think that Justices Breyer, Ginsburg and Stevens will be on a concurring.