I think he's gonna move to Ferrari or Mercedes.
At Red Bull he'd just be the backup to Vettel, and Mclaren have 2 good drivers.
But I think at Ferrari he could give Alonso or Massa a run for their money. I think Alonso AND/OR Massa will leave Ferrari at the end of the season.
And I think at Mercedes he could replace Schumi, and potentially do better than Rosberg.
Or stay at Force India, patiently, and wait for them to become a title-challenging team. (Probably another 2 years until they can be considered for it)