The title of the series is yet to be named. See Changes again for King of Ashes - War of Five Crowns
The King of Ashes was the working title for a new series of books, not related to the Riftwar Cycle. There are currently planned 3 books, the titles of which will be made known at a future time.
No further information is known at this time, though as more is revealed, we will certainly make it known.