Pokemon fans have been waiting for some kind of announcement alluding to remakes of the fourth-gen mainline titles, Pokemon Diamond and Pokemon Pearl. However, no such announcement or direct teaser has ever come from Game Freak or Nintendo, despite it seemingly happening time after time.
The fourth generation of Pokemon games are widely beloved by fans thanks to the new Pokemon added, memorable NPCs, and creative locations. Many would agree that Pokemon Diamond and Pokemon Pearl would greatly benefit from modern enhancements given by the current generation of Pokemon, as well as generations that have come before it, and that's why there's such a deamnd for it.
The only thing going against the hopes for the fans is in how the generation 3 remakes were released back in 2014. While Pokemon: Let's Go, Pikachu and Pokemon: Let's Go, Eevee were released in 2018 with them serving as remakes for the first generation of Pokemon, some fans might worry that the Pokemon remakes are looping back to the beginning with a generation four remake being shelved for now. However, Let's Go is a completely different beast altogether.
While the lack of news and the fan speculation on sequels to the Let's Go games can be very disheartening for those hoping for Sinnoh remakes, it's too early to lose hope. Before the release of Pokemon Omega Ruby and Pokemon Alpha Sapphire, Pokemon HeartGold and SoulSilver were released in 2009. With the Hoenn remakes being released in 2014, there was a solid five years between remake releases.
The current gap between remakes is six years, but that doesn't mean that there's no chance for a remake to come. However, this gap is still worrying. Especially considering the current pandemic, the odds of an announcement for Sinnoh remakes soon is unlikely for 2020; however, if these remakes are in pre-production or proper production, news may come in 2021.
Players should also keep in mind that the Crown Tundra DLC for Pokemon Sword and Pokemon Shield is still in development, taking up some of Game Freak's time and resources. Remakes of previous generations are always are considered to be a part of Pokemon's main line of games, meaning that it may need just as much time if not more than the other mainline games.
The integration of features and Pokemon added after the fourth generation would definitely eat up a lot of development time in both pre-production and normal production due to the struggles of trying to implement improvements as well as keep the original feel of the games intact. Possible changes to the contests of Pokemon Diamond and Pearl as well as the possible implementation of Sword and Shield's wild areas would also be elements that could cause announcements to be delayed.
There would be a lot of fan expectations for Sinnoh remakes if they were released, especially considering the criticism toward Pokemon Sword and Pokemon Shield. However, fans can only hope that Diamond and Pearl are treated with the respect they deserve and aren't so far off that they become nothing more than a pipe dream. It may seem less likely by the day, but the fan demand is high and Nintendo knows how badly fans want this.
There is currently no news on Pokemon Diamond or Pokemon Pearl remakes.