A Spanish site has posted an interview with GameFreak in which they have declared Pokemon Black and White to be the last games in this iteration. Of course this declaration does not impact whether or not we get AquaSapphire and MagmaRuby, but unfortunately this looks like a no-go for Pokemon Grey (or Gray? Or why debate the spelling of a fan-guessed title for a game we now speculate may never exist?). I have my own doubts as to whether anything got lost in translation between Japanese, Spanish, and English, but this is definitely interesting news. Would definitely be ground breaking for the series not to cash in on a 3rd version.
As Serebii and I were discussing though, there is the fact that an interview with GameFreak (in Japan) had said that a third game would go deeper into N’s history and reveal his name. Tackman also points out that there are items and attacks that would seem to coordinate with the third legendary, Kyurem, that are not seen in Black or White. Is this rumor busted? Probably. But it’ll be interesting to see how it plays out.