The information available on Pokémon Legends: Arceus and Pokémon Shiny Diamond and Shimmering Pearl has not been updated since their announcement at the last Pokémon Presents. However, now comes a rumour that would confirm new details about these releases.
These have been shared by Kelios on Twitter, known for correctly leaking information about the franchise in the past. On his Twitter account, he has offered these details on the date of the images shown so far of both games and the status of their development:
The Pokémon Legends: Arceus footage released during the latest Pokémon Direct was shot “in early December 2020”, apparently almost 3 months earlier.
And as for Pokémon Shiny Diamond and Shimmering Pearl, most of the game has already been finished, they’re polishing it graphically and fixing bugs. The screenshots would be from early January.
As for release dates, Pokémon Shiny Diamond and Shimmering Pearl have already decided their release date (I don’t know it yet), and Pokémon Legends: Arceus is “pending”, they will set it later next year.