I still believe the universe itself should have expanded to more books, more characters, K.A. had a dozen ghost writers who could have easily taken over their own mini-series, the ending was a beginning for a larger and fascinating sci-fi world, Andalites and humans starfaring together, (humanity possibly retaining control of a few Yeerk vessels, or buying them off the Skrit-na) the kelbrid, The One, it could have been big.
Well, there's always fan fiction, no?