It would be a monumental d**k move on Kubica's part to break the contract and frankly I can't see why Sauber would need him when Kobayashi is already a rapid young driver. They need some experience and reliability to back Kobi up...That description suggests Nick Heidfeld.

The Frome Flyer: Smoother, Smarter, Calmer,
Winner.
Jenson Button: Professor, Chauffeur, World Champion Racing Driver.