He's lucky he looks to be staying but to me Robert Key would be first on the list to be got rid of. McCullum always sounds like a genius when compared to Key.
I think Key has made a lot of bad decisions- including to appoint Baz as coach for both formats. I think Baz will stay, with perhaps Alec Stewart in Key's role. They might split the role again and keep Baz as one day coach, but I doubt it.
Phil Walker, who admittedly is a huge Essex fan, said on the Wisden podcast that he'd like to see RTD as coach. Prising him from the India set up would be a challenge though, especially since they've just won the T20 World Cup. I'd like to see Jonathan Trott given the test job. If he can cope with Afghanistan, he can cope with England.