-there was no way to transfer pokemon from gen 5. -they completely changed the iv and ev mechanics. -you could only save in pokemon centers -introduction of new types that completely unbalance the type charts -you could only carry 10 of each item.
none of these will happen, but which one would make you the angriest?.
I would hate the 10 item limit and pokemon center saving. --- 3DS FC : 4871-3511-4727