Each time a new generation of Pokémon is released, the games come in two versions. Although the versions feature the same storyline, they typically have specific Pokémon that only appear in it and not the other. For Pokémon Shining Diamond and Shining Pearl, these version exclusives will continue to be important in remastered games. These are all version-exclusive Pokémon that you can catch in Pokémon Shining Diamond.
The information we have comes from the original games. However, these lists may change depending on what players learn as they embark on the remastered journey. Here's what we know right now.
The addition of Ho-Oh, Entei, Raikou, and Suicune comes when we learn about Ramanas Park, a place that players who have reached the end of the game and have had their name in the Hall of Fame can access. They will be able to find both Legendary and Mythical Pokémon, and Shining Diamond and Shining Pearl both have unique encounters. If you're looking to catch all Pokémon from both games, you'll need to trade with another player who has access to that version. It probably means that you will need to go out and capture some of your exclusive versions from your game as well.