Trainers all over the world who are looking towards the next chapter in Pokemon will have a new form of Lycanroc to add to their rotation. Dusk Form Lycanroc was revealed on the Pokemon website yesterday and appears to be a crossover between the current Midday and Midnight Form.
Check it out:
The Dusk Form Lycanroc is apparently using the Midday Form model as a base, but features the red eyes, and added back hair that you see on its Midnight Form. It's also worth noting that the background of the image features a dusk sky, so it's entirely possible that Ultra Sun and Ultra Moon could leverage Dusk and Dawn in a similar way that Sun and Moon used Night and Day.
According to Pokemon.com, you "can't get Dusk Form Lycanroc on your team by ordinary methods, such as discovering the mysterious Pokémon in the wild."
The Dusk Form Lycanroc page doesn't specify how you can get the Pokemon, but more details will be available "soon."
[Source]