I recently did a quick scan through Tamora Pierce's official facebook page (TAMORA PIERCE, FANTASY AUTHOR) to make sure we have all the information for the new books about Numair Salmalín. There are a few changes to past updates. Tempests and Slaughter, recently titled The Gift of Power, will be published on an unknown date in 2018. It will still feature Numair Salmalín while living in Carthak. The new title was released in a facebook post made on November 10th, 2016, and the new publication year was alluded to in a post made on September 30th, 2016. It is unknown if the series title will change completely as well, as in her Nov 10th post, she referred to the new book as Arram #1.
There are sure to be more changes in the future, including to the title and publication date of the second book, currently called The Exile's Gift. The third book is still untitled with no accurate news of a publication date.
If anyone has any more information or questions, please comment below!