Pokémon Scarlet and Violet will almost definitely be featuring a new bull Pokémon in its Pokédex. From what has been seen so far, the yet-to-be-named new region is based on Spain, and speculation of other details regarding the game is already running wild. Amidst all of the discussion, one very plausible theory is that a new bull-themed Pokémon is about to enter the series.
Thus far, what little information about Scarlet and Violet that has been confirmed includes new protagonist designs, some images of the world, and the three starter Pokémon. Most excitingly, it was revealed via Twitter that Scarlet and Violet will be open-world games, greatly shaking up the series tradition. With Scarlet and Violet having just been announced, information on the Pokédex is understandably scarce, but there is good reason for players to expect a new Bull Pokémon to make an appearance in the Gen 9 games.
The first and most major reason for this prediction is the region for Scarlet and Violet itself. Nintendo and Game Freak have been very meticulous with how they design regions based on their countries of inspiration, and culture is a big part of that. The traditional architecture in the Japan-inspired Johto region and large cities of the Now York-inspired Unova are exampled of this. Fans even widely speculate on what country will inspire the next Pokémon region between generations. Pokémon have also been designed based on regional influences before, such as the hula-themed Pa'u form of Oricorio in the Hawaii-influenced Alola region. With bullfighting being one of the most internationally famous aspects of Spanish culture, it would not at all be surprising if a new bull-themed Pokémon were to be introduced alongside the region.
A New Bull Pokemon Would Be A Great Addition To Generation 9
Another argument in favor of a new bull Pokémon would be the Pokémon series' habit of introducing Pokémon that have natural rivalries. Examples would be the mongoose Pokémon Zangoose and the snake Seviper in Gen 3, as well as the metallic ant Durant and fire-breathing anteater Heatmor in Gen 5. While trainers in Pokémon have had plenty of rivals, rivalries between Pokémon can occasionally be more interesting. If Pokémon wanted to introduce a similar sort of natural rivalry, then creating a pair of Pokémon based on a bull and a bullfighter would work perfectly. Taking this into account combined with the Spain-inspired setting of Scarlet and Violet, the argument for a new bull Pokémon becomes even stronger.
Strictly speaking, Scarlet and Violet could also add a new bull Pokémon without introducing an entirely new species. Starting with the Alolan forms in Pokémon Sun and Moon, every generation has introduced some new regional variants of older Pokémon, a tradition that has proven very popular with fans. A prime example would be Hisuian Voltorb, which was popular enough to be the first Hisuian form in Pokémon GO. Scarlet and Violet could introduce a regional variant of Tauros or Bouffalant, the iconic bull Pokémon from the first generation. With many past regional forms proving to be very successful, there is definitely a possibility that a new form for Tauros or Bouffalant could be coming when Pokémon Scarlet and Violet are released.
Although nothing has been confirmed yet, there are several reasons to believe that Nintendo is prepared to release a new bull Pokémon in Pokémon Scarlet and Violet. Considering the setting and Nintendo's past habits with the franchise, it would not be unexpected at all. There will not be a definite answer until additional info is shared - or until the games release at the tail end of 2022 - but there are several strong reasons to believe that a new bull Pokémon is on the horizon.