While the Pokemon series isn't known much for experimentation, typically sticking true to its core formula aside from adding occasional battle gimmicks like Mega Evolution, Z-Moves, and Dynamaxing, players were thrown a bit of a curveball last year. In January of 2020, it was announced that Pokemon Sword and Shield players would receive the first ever mainline DLC expansions: The Isle of Armor and The Crown Tundra.
The announcement came just 2 months after the initial release of Pokemon Sword and Shield, and when it was later revealed that The Crown Tundra would be releasing in the Fall of 2020, fans took that as a sign that Game Freak likely wasn't going to release an annual title that year, breaking a 4-year-long trend. And although The Isle of Armor and The Crown Tundra have been available for some time now, rumors have continued to swirl about a possible 3rd DLC expansion for Sword and Shield.
Pokemon Sword and Shield's Return to Kalos
Back in October of 2020, rumors began to spread about another Pokemon Sword and Shield DLC expansion possibly taking players back to the France-inspired Kalos region. Since Kalos and Galar are both based on real-life European countries, it makes sense that they might be close in proximity in the Pokemon world as well. Early rumors stated that Galar's train might be used to travel to Kalos, though fans now know that it is used to travel within the region and to The Isle of Armor and The Crown Tundra.
Other rumors are based on the Mythical Pokemon Meltan and Melmetal, which are believed to have been first seen 3,000 years ago, the same time period as the Kalos Pokemon War, that is, if Pokemon X and Y and Pokemon Sword and Shield even fall within the same timelines. And considering that Melmetal's Pokedex entry also states that it has returned for "some reason," fans have believed that it might play a significant role in the connection between Galar and Kalos. Other rumors involve landmarks like the Galar Mines bearing a resemblance to Kalos' Glittering Cave.
Pokemon Sword and Shield: The Scepter Sea and The Cinder Citadel
In September of 2020, supposed leaks began to surface of much more specific rumors for Sword and Shield's next DLC expansions. These leaks include expansions known as The Scepter Sea and the Cinder Citadel. The Scepter Sea expansion was rumored to be based on the real-life country of Wales, would bring new Gigantamax forms and G-Max moves to the Pokemon Scizor and Steelix, and would introduce the new Water- and Ground-type Legendary Pokemon Mersanobra.
While The Scepter Sea has been rumored to release in the Summer of 2021, it is said to be followed up by another expansion titled The Cinder Citadel, which would be based on the real-life country of Ireland. This particular expansion has also rumored brand-new Gigantamax forms and G-Max moves for Pokemon like Boltund, Aerodactyl, and Falinks, a new Fire- and Dragon-type Legendary Pokemon known as Inferagon, set to release in Fall 2021.
A separate rumor about The Cinder Citadel also mentions that players would be taken to an area filled with empty castles and dilapidated ruins, where they would meet a new professor known as Mr. Wyman. Fans would see Galarian forms for the Sinnoh region starter Pokemon Piplup, Turtwig, and Chimchar, as well as Hitmonchan, Hitmonlee, Hitmontop, and Bisharp. This rumor however mentions that the DLC's signature legendary would be Rock- and Dragon-type as opposed to Fire- and Dragon-type.
The Most Recent Pokemon Sword and Shield DLC 3 Rumor
While most every Pokemon Sword and Shield DLC 3 leak and rumor gained traction around late 2020, there is one supposed leak that has gotten attention only just recently based on its accuracy. Posted over on 4chan all the way back in February 2020, a leaker correctly predicted that The Isle of Armor and The Crown Tundra DLC expansions would bring an additional 200 Pokemon to the games. It also correctly predicted that the Pokemon Diamond and Pearl remakes would be coming in 2021, and that they would be simple remakes.
This February, fans finally got their first look at Pokemon Brilliant Diamond and Shining Pearl, which are taking a much simpler, more faithful approach to remakes when compared to past titles like Omega Ruby and Alpha Sapphire. Supposedly, Sword and Shield's 3rd DLC would add the rest of the missing Pokemon from the National Pokedex to the games, in addition to adding 3 brand-new Mythical monsters. Additionally, the idea of Sword and Shield's 3rd DLC existing alongside Brilliant Diamond and Shining Pearl may not be too far-fetch'd.
This is mainly because the 4th generation remakes are confirmed to be developed by Pokemon Home developer ILCA, as opposed to Game Freak, which fans now know is focusing its own efforts on the upcoming Pokemon Legends: Arceus. Finally, this leak mentions that a "Project Kingin" will release in 2022. Interestingly, this lines up with the release window for Pokemon Legends, which is slated for an early 2022 release date. It may also be worth noting that the Japanese word "kingin" roughly translates to "gold and silver," so it will be interesting to see if Pokemon Legends reveals itself to carry any sort of  motif along those lines.
Pokemon Sword and Pokemon Shield are available now on Nintendo Switch.