Revealed alongside game release
Two more Ultra Beasts, both codenamed UB-04, have been revealed by the official Pokémon Sun and Moon site. These are the Ultra Beasts that were revealed in this month's CoroCoro Comic. The official Japanese Pokémon YouTube channel also released a promotion video along with this reveal.
The orange and white Ultra Beast that resembles origami is codenamed UB-04 Blade. The metallic green Ultra Beast that resembles a tower with arms is codenamed UB-04 Blaster.
These reveals coincide with the official release of Pokémon Sun and Moon worldwide (except in Europe). For further details on these Ultra Beasts, please see the Bulbapedia pages for UB-04 Blade and UB-04 Blaster.