Similar to the last trademarks; V Star and Matchless Fighter, Silver Lance, and Jet-Black Spirit/Poltergeist, this falls under the same category as other Pokémon TCG sets.
This trademark seems to be more related to a new gameplay mechanic and new type of Pokémon card. The font formatting is similar to that of V and VMAX cards and the V Rule found on the bottom of those cards.
This could be a new type of card similar to the Sun and Moon Tag Team cards, or it could be a new Ability/Rule where two Pokémon combine like Calyrex V with Spectrier V and Glastrier V.
Update 12/14/2020
There will also be a V-Union Box released on September 24th, 2021 and a second box with the 25th Anniversary Products on October 8th, 2021.
