There are only two teams better than the Poms right now and we know that India tend to struggle in the Australian conditions, I very much doubt they could have wiped the floor against an Australian team that boasts Johnson in the form he's in.
There are concerns at the top, but I'd argue that right now is the worst time to do it. What kind of message are you sending the team? Gee, thanks for the winning the holy grail in Test cricket and now it's time to listen to the cuts.
Watson. Cut
G. Bailey Ohhh you better believe you're cut.
Smith I don't like you because you're from NSW, so you're cut too.
Alright team, now please make welcome a bunch of players who have been slightly tapping on the door this season! Hundreds? Who needs 'em when they're from Queensland!
If a player gets injured, by all means but let the Australians enjoy their success and consider changes in South Africa.
If it was any ol' Test series, I'm sure blooding a player or two in the dead rubber would seem appropriate, but this is the Ashes. Let the Aussies savour the moment.