The actor didn't know he wasn't part of the sequel until he read about it in the press. Even though he knew the second part would have new faces, he wasn't ready to be replaced.
The actor has been telling people how it was unprofessional on the director's part to go to the media before telling him.
However, the director has been telling people the reason he took Akshay is because the story takes a leap and Emraan wouldn't have looked the part.