I'm sure that Grissom would never 'dump her ass'. He's not like that. Sure he's probably hurt and confused, but he knows Sara better then anyone, and he'll back away if that's what he has to do to make it better. With time I'm sure if Sara comes back, Grissom will have no problem working things out with her. After all, it's Grissom and Sara we're talking about. They're just meant to be.