So I just realised I'm 9 years late but if Aqua didn't save Terranort at the end of BBS then technically, from what I know of kingdom hearts, the games/the story with Sora shouldn't exist the way it does. Sure there is the 'Xehanort plans for every eventuality' but that means terranort would be in darkness, aqua would wake ventus and sora shouldn't have the keyblade. Because terranort doesn't get saved by braig and therefore no further studies of the heart and no terranort to halve into ansem and xemnas, organization 13 shouldn't exist. Xehanort from the past probably wouldn't have gone to destiny islands which means the keyblade wouldn't transfer from Riku to Sora because no darkness and so that means... what?
I doubt any of this would happen but this is my understanding