The T6 will be a van -therefore it will look like a van therefore any other versions, California, Multivan etc will be based on the T6.
Van's as a rule place practicality first.
The only way I could see this being different if VW decide not to base the next California/Camper on the T6 and it becomes a model in its own right.
i could see a market for this in Europe but not in the UK.
By the end of the T2 in the late 1970's it was frankly rubbish, so the leap to T3/T25 had to be big and it was and it wasn't that difficult to make something that appeared fairly advanced against the last T2's, likewise the T4 was a very good van and by its launch in the early 1990's the standard of vehicles was much better.
Cars and Vans in real terms are much better, therefore the leaps in design are less and the changes tend to be mechanical or technology based.
VW have developed an evolutionary approach to design because it suggests or is meant to suggest confidence and quiet understatement. If a car is good, it shouldn't to shout about it, right? That's the idea I think lol.
As i remember the Microbus and other retro style campers/buses were designed with the American market in mind.
James