Along with searching for Pokemon for you to catch, the upcoming Sun and Moon will have the player collect Zygarde Cells. When approached by Dexio and Sina from X and Y, the player will be given a Zygarde Cube, which in turn can help them collect Cells and Cores scattered around the Alola region. The two of them will show up throughout the story to check on your progress, and no doubt to give you more information on Zygarde as well.
Also, you remember that cute little game Pokemon Snap from a while back? Well, now that’s returning in Sun and Moon thanks to the Poke-Finder. You’ll once again be able to take pictures of any creature you come across in certain areas of the game, and submit them for evaluation. The better pictures you take, the more features will become available, such as the ability to zoom in.