If you happen to have a Japanese Wii and a copy of Pokémon Platinum on the DS, you may have discovered that My Pokémon Ranch does not interface with the new continuation of Diamond and Pearl. Pretty short-sighted of Nintendo, or Game Freak or Ambrella! We wouldn't expect Platinum to be that different.
In any case, Nintendo has announced via the official Pokémon site that an update for the WiiWare Pokémon storage device/game is forthcoming sometime this year, to allow connection between the game and Platinum. Also according to the Pokémon site, there is no issue with connecting Platinum to Pokémon Battle Revolution.