If we function under the assumption that the voice talking in both 4.4 and the trailer is Arbert, it feels to me like it's more plausible that the first shard effectively is the future of the source due to being extremely similar, which would make simply preventing what happened there from happening again "rewriting history". I'd kind of rather they just stick to having a multiverse instead of throwing time-wimey stuff into the mix as well.
I'm also thinking we might end up becoming the Warrior of Darkness simply due to needing to fight back the excess light and the beings born of it at the first shard as part of a plan that will spare both it and the source from destruction, with the mystery girl likely being a key player judging from her seeming presence on the collector's boxart.