I can't see the meta changing like it did from gen 3 to 4. Its the same game, but with more pieces and as you say, they seem to offering alot of back catalogue support.
My main concern is that tiering will be a nightmare with so many pokemon with one or two hyper stats but mediocre other stats.
Also, some of these new pokemon pose such new and strange stat-typing threats that old school offensive threats will probably beast early defences ^^