Ok,real leaks:
Zygarde will be present under the tree of life located in the fourth island of Alola.
No new Mega Evolutions.
The starters will have different types.
In Pokémon Sun the day will be crucial for certain functions, in Pokémon moon the night.
Marshadow will be dark poison.
Rockruff will have different evolutions.
There will be eight captains.
There will be references to any Pokémon game.