There is no way Trump would keep Kelly or McMaster or anyone unless he has a reason to keep them. Each of his cabinet and staff serve a specific purpose. Once that purpose is done, they are no longer needed and are cut loose.
Now, whether or not they are loyal is another thing entirely, but Trump could be using that to his advantage to see who is loyal who isn't.
However, Kelly, McMaster, Mattis, all the generals are important and vital. If Trump couldn't trust them he never would have put them where they are.
He is not going to put himself in a position to fail the country, the people or himself.