I always wondered...When they were trying to excuse all the restrictions in place on Pokebank, one of the things they said is that they plan for it to be a very long-term service. It seems likely they'll go the time capsule route at the very least.
In Pokebank, gen 5 is blocked from it and can only transfer to it and not back. Gen 6 can use it transfer to it and take it back as well. When gen 7 comes, how will Pokebank be? Will gen 6 be introduced to limits such as only being able to use boxes 1-10 (whilst gen 7 can use the rest)? Or will gen 6 see gen 7 pokemon as ? Pokemon that cannot be transferred?
it is mind boggling! lol