Well, it would actually impact a number of characters. For instance, Orde, Chiara, and Zaria would not exist, meaning all of the events associated with their characters in the past (such as the reason for Ce-Matoran being female) would be decanonized. Additionally, everything having to do with the Bota Magna Vorox, the Red Star revelations, and Velika's secret identity would be wiped out.
I agree that Journey's End is a fitting conclusion to the G1 story, but there's no need to decanonize what came after it just because it's unfinished. The same could be said of TV shows such as the Clone Wars, which was canceled while one season was in production. Even though the ending of the fifth season was an adequate and emotional conclusion to the show, the fans were still pleased to have the episodes from Season Six, despite the fact that they weren't part of an official ending. Lots of great stories have been left unfinished, but that doesn't mean that things need to be wiped from canon in order to make it seem like the loose ends are tied up. Part of BIONICLE's beauty is that it was created as a story that fans could influence and interact with, so I personally believe that leaving the canon intact is a good thing, as it allows for those fans who want to imagine how the serials would have ended to do so.