Update 10/3: Game Freak has clarified that there won't be 18 gyms in Pokemon Sword and Shield.
"In the Galar region, Pokémon Gym Battles are popular sporting events, and the 18 different types of Gyms that exist in Galar contribute to the background setting of the story in Pokémon Sword and Pokémon Shield. In each game, Trainers must collect eight Gym Badges to complete the Gym Challenge and earn the opportunity to participate in the Champion Cup.
Over the course of the main story, Trainers will challenge eight Gyms, which are all in the Major League. Which Gyms appear in the Major League and Minor League will differ between Pokémon Sword and Pokémon Shield. For example, depending on the version of the game, Trainers will be able to challenge different Gym Leaders, such as Bea or Allister.
Each version will have eight Gyms and eight Gym Leaders that Trainers can battle for a traditional Gym Challenge experience that fans have enjoyed throughout the Pokémon video game series."
Original story follows.
Pokemon Sword and Shield are the first mainline Pokemon RPGs on a Nintendo console, something fans have been wanting since the release of Red and Blue on the original Game Boy. Game Freak is set on making a number of major changes to the formula for the eighth generation to set Pokemon Sword and Shield apart from the rest of the series and it appears that one of those changes is going to affect Pokemon Gyms.
Pokemon Sword and Shield are the feature games for Game Informer's November issue, meaning that a whole lot of information is starting to spill out like the complete removal of HM Pokemon moves. And now new information has been released regarding the way gyms will work in Pokemon Sword and Shield.
Fans of the series will be used to the familiar Pokemon Gym structure, where players must defeat 8 Gym Leaders in order to earn badges and compete in the Pokemon League. It appears that in Pokemon Sword and Shield, there will now be a total of 18 Gyms for players to battle across different leagues, and the Elite Four has been replaced for a new Championship Cup system.
"There are to be 18 gyms in the game with different gyms being in the Major League and different in the Minor League between game version, for example, Bea's Fighting-type Gym is in the Major League in Sword while Allister's Ghost-type Gym is in the Major League in Shield. The idea is that the gyms can be in different leagues each year in the Galar Region. It's currently unclear if all 18 will be battleable"
Not only will Pokemon Sword and Shield feature more gyms than any other game in the series have before, but there will also be two different leagues in the Galar Region that are said to change and rotate each year. Just like with version exclusive Pokemon, the gyms will also change between Pokemon Sword and Pokemon Shield, which potentially leads to much more replayability for fans that purchase both.
Right now, more information is needed on exactly how the Major League and Minor League are structured and what constitutes as a year in the Galar Region. For now, the idea has a lot of potential, particularly the high number of gyms available - something that hasn't been seen since the second generation.
Pokemon Sword and Shield release on November 15, exclusively for the Nintendo Switch.
Source: Game Informer (via Serebii)