Planned succession? Isn't that what the developmental squad is for?
There are no "old" players in the England team. All have minimum 3 years age-wise at least of professional cricket, if not international.
Is this just not a great big case of over-confidence and too much expectation?
Look back at Ashes of recent history in Australia. Apart from the most recent trip, it is lost 5-0, lost 4-1, those types of results. It feels bad now, but in a year or two, it will be no different than the other trips.