a. With regards to the OP's actual question: I've read that info, too, but only on TVTropes... I'm not sure where it originally came from. I suppose someone could ask Greg in the currently-running LMB topic.
I've just remembered this topic, in which other possibilities for the story were discussed in some detail. Don't post in it as it's almost two years old.
Yes, the Toa Inika were planned to go to Karda Nui, IIRC. However, I think I also remember that the Toa Nuva were intended to start in a three-year trilogy immediately thereafter. Kinda glad that didn't happen, since it would have dragged on and on... the pacing of 2008, I think, was a lot better than a three-year slog to reawaken the Great Spirit would have been.
Keep in mind, OP, the linked topic doesn't actually include any official plans or information, so I don't think it's what you were looking for.
c. No discussion of the original story plans can be complete without BIONICLE #5. 2010 was going to feature the Valley of the Maze, and 2011 would have been set on Bota Magna. Obviously, that didn't happen, and I don't think I need to explain why.
Edited by Yaldabaoth, May 26 2014 - 10:49 AM.