Dudes, remember, the new Pokémon/formes are being revealed AFTER the release of Platinum. This means there are two possibilities:
- They DO appear in Platinum. This means they HAVE to be alternate formes (not new Pokémon), and, since they're not supposed to be known until Sept. 28 through Nov. 4, the alternate formes would HAVE to be hidden (event-triggered, password-protected, or some other form of keeping them hidden, though I think event is the most likely, being a main Pokémon game and not a spin-off like Ranger or Mystery Dungeon). What I think is that, if this is the case, the items to change Pokémon X into these new alternate forms (think Glacidia Flower) would be handed out through events.
- They DON'T appear in Platinum, and rather are Gen V Pokémon. This means they don't necessarily HAVE to be alternate formes (although it doesn't rule it out, either). I think it's weird that they would be releasing new Pokémon (or forms) if they're not gonna appear in the next game, but the fact they will be revealed AFTER it releases makes me suspicious.
Although not as likely as being alternate forms, I think they still have a considerable chance of being new Pokémon.
As for what the Pokémon actually are, well, I saw Rotom like everyone did, and not much more...