Brandon Sanderson has completed the first draft of Oathbringer, the third novel in The Stormlight Archive sequence, following on from The Way of Kings (2010) and Words of Radiance (2014).
The novel will require extensive rewrites and editing before publication, which is currently scheduled for November 2017. The novel currently clocks in at 461,223 words, which is actually too large to be published in one volume. Sanderson anticipates the word count to come down in the edits, so the novel is reduced to something more easily publishable.
If the current word count stood, it would make Oathbringer one of the longest fantasy novels ever written, behind To Green Angel Tower by Tad Williams (520,000 words), Ash: A Secret History by Mary Gentle (493,000) and The Lord of the Rings by J.R.R. Tolkien (473,000) but ahead of A Storm of Swords by George R.R. Martin (424,000) and Sanderson's own Words of Radiance (just over 400,000).
Oathbringer is the third of ten planned novels in The Stormlight Archive sequence. Sanderson's original plan was to release the books at 18-month intervals, but the actual release dates are working out at between three and four years per book. If Sanderson is able to release each future book at precisely three-year intervals, that means that the series will not completed until 2038, or twenty-two years from now. However, it would be considerably longer than this since Sanderson plans to take a long break between Books 5 and 6 to write the Mistborn II trilogy, pushing the completion of the Stormlight series comfortably back into the 2040s.
It'll be interesting to see if Sanderson (who turns 41 next week) starts making the books shorter or reduces his other projects to get Stormlight done faster, or if he accepts that this is just how long the books are going to take.
The writing time of the Stormlight books may also become problematic if DMG Entertainment's planned film adaptation of Sanderson's Cosmere mega-series (which Stormlight is just one part of) is a big success and they want to start cranking the films out faster. But we'll see how that goes.