Drawing from the press conference, I feel that Marrone is a methodical guy and is gonna watch game film and see what needs to be fixed. Of course it seems obvious that some coaches need to be replaced/added (Crossman, QB coach), but he may feel that he can fix problems he sees without lopping any heads off (whether that's the right choice or not).
If he's gonna fire any coaches, its going to be after he reviews game film and talks to his staff.