If the play of this secondary remains as it has, no one will be going anywhere. It will get figured out. These guys each fit a certain role that supports the other.
All of them can bring the wood. All of them can support the run stopping aspect of the defense, but ET has range like no other. If you watch him live at a game and focus on him, he can get anywhere from anywhere. Kamtrack is like a LBer that can close. BB is a freak of nature that muscles dudes to the ground frequently and Sherm is all over his guy on every play, literally letting his guy run in hopes that the QB throws his way.
Simply put, they have all the basis covered. Remember, outside of BB, these guys are just kids and BB has low NFL miles. They can still get better. JS is a magician, he will make it work if it is possible while they supplement the line with youth. I honestly believe that PC has 2 more years of kids he has been scouting from his USC days to get LBers and Dline guys. I think we are likely to see changes there before the secondary.
However, there is quite a stable of DBs to pick from, but ET is the reason the corners can get away with so much. He is a must have. Don't even want to think about the future money, I am going to enjoy it while I can.