I hope the remake/third version schedule follows Generation III (remakes before third version) rather than Generation IV (third version before remakes). It seemed like they just shoehorned Platinum in right before the much-hyped HG/SS, completely diverting attention away from Sinnoh too quickly...
With RSE & FR/LG, FRLG seemed like "Hey, you get to revisit Kanto after so many years! What a treat, eh?" followed up by "Don't forget, Hoenn still has more surprises in store for you! ;)", which gave one an incentive to revisit Hoenn (then again, FRLG's replay value was a bit small compared to that of Emerald's).
With DPPt & HG/SS, though, it seemed like "Hey. I'm Platinum. Might as well get Sinnoh over with. I have a few new features, though. I bet you think those rumored GSDS games won't get released now, eh?" followed up by "Hey! GSDS IS REAL!!!!1!!1! Sinnoh is old news now! It's time to head back to Johto, the region of pure awesomeness and EPIC WIN!!!". I don't have Platinum or HeartGold yet, but it seemed like Johto dominated Generation IV in the end while Gen III was a nice mix of Hoenn and Kanto, with Hoenn arguably gaining more time in the spotlight. Johto just hogged the spotlight in a Gen where it was supposed to slightly remain backstage...
With Generation V, if Game Freak chooses to go the Gen III route, the third version is going to have to be chock full of new features (which can easily be by fixing the majority of BW's cons like PokeDex interface, Select Button feature, moving multiple Pokemon, restoring the Follow-Me feature, bringing back actual Pokemon Contests and the Pokeathlon, etc.)