How do we know that? We could be getting both. It's implied through this tweet by the screenwriter of the animations, Merlin Mann, that he'll be no longer writing for Bionicle. From there, one can assume that the animations won't be continuing. Also, he gives a reply in the comments regarding the fact that the battle with Skull Basher was meant to be a whole episode, but was shortened due to time-consumption. He said he won't be writing. It's not too unlikely that someone else will be. Granted, we don't know if the possible replacement would be better or worse.