Back on August 18, 2021, the newest trailer for Pokemon Legends: Arceus was released during the day's Pokemon Presents livestream. This trailer showed off new Pokemon and regional variants for the game's Hisui region. Understandably so, some are curious about how this may connect to the also upcoming Pokemon Brilliant Diamond and Pokemon Shining Pearl.
At first, the Hisui region in the upcoming Pokemon Legends: Arceus may seem unrelated to the Sinnoh region in Brilliant Diamond and Shining Pearl Pokemon games. This however is untrue, as the Hisui region is actually the Sinnoh region's original name when it was first being settled by humans. This means that the two regions are actually the same location, just in different time periods.
Keeping this in mind, there is a possibility that the new Pokemon and regional variants could make appearences within the upcoming Sinnoh remakes. Before getting hopes up however, it's important to look at all the details that are currently known about all three upcoming Pokemon titles.
As of the new trailer, the only confirmed Hisui regional variants are Growlithe and Braviary. This most likely means that Arcanine and Rufflet will additionally obtain Hisui forms, but no images of them have been made public at this time.
In addition to these Pokemon, new evolutions for Stantler and Basculin have been confirmed for the Hisui region: Wyrdeer and Basculegion. Because of these Pokemon, there is a large liklihood of the original Pokemon getting Hisui forms to go along with their new evolutions, but these are still unconfirmed as well.
The biggest piece of evidence against the Hisui forms appearing in Pokemon Brilliant Diamond and Shining Pearl are the release dates of all three games. Looking at the recent livestream where the new trailers were shown, the Sinnoh remakes will be released on November 19, 2021. Meanwhile, Pokemon Legends: Arceus is set for a January 28, 2022 release date, two months after the Sinnoh remakes.
Considering that the Hisui regional forms have only been shown in the trailer for Pokemon Legends: Arceus, it is clear that these Pokemon are meant to make their premiere in that game. With Brilliant Diamond and Shining Pearl coming out much earlier than Legends: Arceus, odds are that the Pokemon won't be appearing in those games, at least on release. It could be possible for an update after Pokemon Legends: Arceus' release, allowing the Hisui Pokemon to appear, but this is yet another thing left unconfirmed.
With how far back Pokemon Legends: Arceus will be taking place in the Pokemon series timeline, there are a lot of events that can occur between the ancient Hisui region and the modern Sinnoh region. Considering how human settlements in real life have led to the extinction of many different species of wild animals, there is a chance that the Hisui forms and Pokemon are now extinct.
Extinction isn't unheard of in the world of Pokemon. It has been a part of the series since the very beginning with the fossil Pokemon. Some Pokemon have additionally been noted to have been nearing extinction or endangered statuses in the past, like with Lapras. While the Hisui Pokemon won't likely all disappear by the end of Pokemon Legends: Arceus, the in-between years could have led to these Pokemon all dying out.
If the reason behind these Pokemon not appearing in Pokemon Brilliant Diamond and Shining Pearl is because of extinction, there could definitely be some side content or extra lore added within the games themselves. As more newly extinct Pokemon, there wouldn't be any fossils of the Hisui Pokemon that can be revived in the Oreburgh Mining Museum. Some towns could additionally hold legends of these long gone Pokemon with hopes of them returning once again.
An important thing to take away from Pokemon Sword and Shield is that the Pokemon series will likely continue releasing DLC packs for games post-release. This makes it possible for Pokemon Brilliant Diamond and Shining Pearl to also get DLC after its initial release. If this were to happen, the Hisui forms and evolutions have a chance to come to these games after the release of Pokemon Legends: Arceus.
A lot of the story within the original games revolves around the legends and history surrounding the Sinnoh region itself. The upcoming prequel will definitely be exploring this as well, but DLC for the Sinnoh remakes could have players encounter the Hisui Pokemon for themselves in the modern Sinnoh region. This could also serve as a way to have players properly encounter and capture Arceus, who is normally not available in the original games without events or an unused item.
Even though these games are being developed by different teams and being released on different months entirely, it is very likely that they will connect in some way. Both games taking place in the same region, but in different times has the potential for a lot of different ways to interact. After all, it would be a waste to not make use of how the two dueling elements of Diamond and Pearl are Time and Space itself.
With the Sinnoh remakes being released in November, there isn't too much time before players will be able to experience the games for themselves. There is still plenty of room for a new trailer for Brilliant Diamond and Shining Pearl to be released, but that isn't guaranteed by any means.
It remains incredibly unlikely for any of the new Hisui forms or evolutions to appear as catchable Pokemon in the Sinnoh remakes, at least at launch. The new Pokemon introduced for the Hisui region probably won't be showing up in completely different title before their actual game's official release. If they were to appear, they likely would have been shown in the trailer for the Sinnoh remakes first, instead of the Pokemon Legends: Arceus trailer.
The upcoming months have a chance to introduce players to a few more Hisui forms and evolutions before Pokemon Legends: Arceus is released worldwide. This information may also lead players to discovering just how exclusive these Pokemon will be to this upcoming game.
Pokemon Brilliant Diamond and Shining Pearl will release on November 19, 2021, for Nintendo Switch.