It looks like Horner signed with Rock Racing. That's the old rumor that has shown up again.
A previous Velonews article on cross quoted Horner as saying he was done with Predictor. Slipstream just announced that they finalized their roster.
While I'm sure Horner will be a terror in the US next year, I'd rather see him breaking legs in Europe. I still don't think he has reached his full potential on that side of the pond.