i think the dark would could make a return. Considering though that its no longer the Dark Realm, is the Sacred/Golden Land. I could see Link returning there if they were to bring Gannon back into it somehow as that is where we left him when slaying him, Link simply wished for things to go back to the way they were if Im right, so i could see this being about preventing Agahnim from pullin his bull crap, cuz that wish almost implies something along the lines as Zelda did for link at the end of OoT, sending him back, Link warning her and link moves on. Just because this is ALttP2 doesnt mean it has to be the same world, It will probably be after the events of the wish, and all the sage decedents would be returned, im guessing they will be who we are searching for in this game to warn or save them from Agahnim. I could be getting carried away but makes sense to me, or i could be misinterpreting what the ending of ALttP implied. But finding those girls could take us outside of the original Hyrul area of ALttP, and if the story included us being too late for some of the decedents we would have to go to the dark world and save them now wouldnt we
They CAN NOT leave the dark world out of this, it wouldnt be and ode to ALttP like they claim. And any Zelda game with a Dual World is instantly awesome. Anyways thats what i think about the dark world!