When Maersk developed the K class at 318 metres, this was modified by adding 2 extra 40' bays into the design which then became the 347m "S" class. Further modifications took place to the "S" class and the result was the 367m "G" class.(although with the G class, the modifications were more than just adding length)
With this previous evolving of a class, I would think it is highly likely this may happen to the Triple E's