As reported by others, GRRM has revealed some information from The Winds of Winter at Worldcon, and read from a chapter early in the book (one delayed from ADWD). He reveals two key events were delayed from the end of ADWD which should occur very early in TWoW: Spoiler As speculated by many, two large battles will take place early on, a 'battle of ice' (presumably at Winterfell) and a 'battle of fire' (presumably at Meereen). A third battle has been added, namely the assault on Storm's End by Jon Connington's forces. Originally this was going to happen off-page, but GRRM decided it really should be shown. Possibly because we've seen Storm's End under siege forever and it might be cool to finally see the place under full-scale assault. He also read from a TWoW chapter (VERY spoilery): Spoiler A chapter featuring Arianne Martell arriving at Griffin's Roost. Prince Doran immediately dispatched her upon news of Aegon's arrival to learn more. Startlingly, Storm's End has apparently already fallen, triggering chaos and forcing the Tyrell army to march from King's Landing earlier than expected. GRRM has said that the chapter featuring the battle at Storm's End is yet to be written.