The reason why I predicted we won't have a traditional 3rd version for Black and White is because I couldn't think of a name for w/e the 3rd version will be. "Gray" would not make sense. Reshiram/Zekrom are based on the Taoist concept of Yin-Yang duality, logically to make a '3rd' version we have to get in between that. Except we can't without going to the highest level, Wuji. Granted that's what Kyurem is, but yeah.
Granted, I didn't exactly predict a B/W 2 either. But that's besides the point.
-User Name Origin: http://www.youtube.com/watch?v=tO_5esMq2kE#t=56s "Japanese Wii U. American Wii U. The future is yours, Xenoblade U."