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From the preview chapters it's evident (for anyone who has read every book in the Cosmere) that Sanderson is bringing in the rest of the systems to this conflict. The use of Alomantic metals with fabrials, the revelations regarding the nature of Returned via Vashar/Zahel, 17th Shard and Ghost blood ties as well as Mraize likely being from Nalthis due to his Breath awareness of an observers presence, Gavilars prologue hinting at world hopping, etc. If I had to guess I'd say that Dalinar will ascend and take the shard of Honor, the nature and intention of Cultivation revealed, and Odium likely shattered. Hoid will obviously come to the forefront of the conflict for the first time during this arc. The fate of the protagonists will most likely be tragic, albeit with some form of redemption and silver lining, it is heavily hinted that humanity and the non fused singers will come to some form of tentative peace as well. Sanderson is a master at putting a puzzle together and reverse engineering it in his stories. Using logic you can piece together a good amount of this. Outliers that have no determined role as of yet; the nature of other world involvement, Shinovar, Iri, Aimia, New Natantan, Uvara Island, surviving humans on Ashyn, remaining Heralds, and all the other things Brandon has in his head that he has hinted at but that I haven't put together. If I had to guess books 6-10 will be on a much grander Cosmereological scale. He will likely have released a second Warbreaker, a follow-up to Elantris, and have started the third Mistborn series. One thing I'll bet on is that an advanced spacefaring Scadiral society makes contact with Roshar, and begins a conflict with Harmony and some element on Roshar. It's really hard to ponder that far ahead though.