In The Games Department
Pokémon Ultra Sun & Ultra Moon
Following the leak of the Famitsu Interview, The Pokémon Company International have confirmed that Mewtwo and other Legendary Pokémon will be available in Pokémon Ultra Sun & Ultra Moon through the Ultra Wormholes. At present we have no further details, screenshots or video but we'll provide full details as and when they come
Edit @ 14:46: When speaking to IGN, game producer, Shigeru Ohmori has also confirmed that Pokémon Ultra Sun & Ultra Moon will be the final main series Pokémon games on Nintendo 3DS, representing a culmination of their work on the device. Back in June, The Pokémon Company CEO, Tsunekazu Ishihara revealed that a main series Pokémon game was in development for the Nintendo Switch, due for release in 2018 or later.
So yeah, guess they went to borrow stuff from OR/AS post-game, which is great. (Now to make sure I have all of my Synchronize 'mons in box when needed)
But...they did say it's the last 3DS game, so they're going all out now. (And now I need to buy the Switch [or soon]; rip wallet)