Not releasing a third version is really the best decision Game Freak could make in this situation, I think. With the release of the 3DS in March, the DS will become a "dead system" - few companies, if any, will be developing new software for it; all the attention will have shifted to the current generation handheld. If a hypothetical "Pokemon Grey" were released for the DS two years later (to follow the release pattern), it would be a poor move on GF and Nintendo's part. A new DS games two years after the release of the 3DS? You don't need a lot of marketing savvy to see it's a stupid move. And if "Grey" were released as a 3DS title while still being obviously built on B/W's engine, any idiot could see it was just a DS game with a few throw-on enhancements to justify calling it a 3DS title. It would be a ripoff, and consumers would know it.
If the interview is to be believed, GF is doing the right thing by focusing on other projects or moving on to the next gen right away. Ideally, what I would love to see them do is experiment with 3DS programming by making either a Ruby/Sapphire remake, or a non-Pokemon project for the system, like maybe a Pulseman sequel or remake (well, we can hope =D ). While we're kept satisfied with those projects, GF would also be working on Gen VI; which, ideally, would be the Gold and Silver to B/W's RBY. Gen VI could be set in southern Connecticut, South Jersey, Pennsylvania or upstate New York; and Unova could be visited after completing the main storyline. Elements like renegade Team Plasma members, the God Stone, Kyurem's hidden moves, and N's past and future could be explored WITHOUT the need for a 3rd version, which seems like a win/win situation for all involved. We get a new gen and we're not fleeced by a painfully obvious money grab in the form of an outdated game on the 3DS or a game released for a dead system, and GF gets what it wants more of - money, money, money. :)
