People. The translation seemed to suggest that both Pokemon are indeed in both games. If so, it will most likely be like Ho-oh and Lugia - you catch the game's mascot first (as part of the story) then catch the opposite later, at a higher level.
Also, Pokemon following you and the Pokewalker were things exclusive to HG/SS. They were nice features, but it'll really be no surprise if they're not included. Particularly the Pokewalker.
EDIT- Also, the 3rd game in this gen will almost inevitably be made for the 3DS, so if you complain about the graphics now (when really the DS can only do so much), just wait until it comes out.