The trailer, which you can check out towards the bottom of this article, comes from Weibo.com (via Surrenderat20). The description underneath that video doesn’t offer much information, but a translation via Google says that “the two sisters born in the spirit of justice, ech chose the opposite path.”
That speaks to the characters’ lore, in which Kayle took a far more righteous path than her sister. The trailer shows off some similar, but very much updated visual appearances for the new characters, as well as showing off the elements of their kits that will have changed. It looks as though Kayle will now have a line-based skillshot, as well as a change to the AoE affect which is currently attached to her E, Righteous Fury – that now looks a little more like the effect attached to Titanic Hydra.