Nakajima can develop a car very well, thats why they keep him, he actually is the one that made the car alot faster(by giving good feedback etc.)
I rather see that sutil is the next one to disappear, he made enough stupid mistakes and im ois actually worse then Piquet. People said that after the deal with Mercedes you could take the teams serious, well you cant, with two of such drivers, Fisichella is at the end of his career and Sutil cant finish a race normally and always has to throw away points.