I just noticed that Tamora Pierce has made another post on her public livejournal. In it she gives some details concerning the future short story collection, Tortall and Other Lands: A Collection of Tales, which is scheduled for publication in February, 2011.
These are the already published stories featured in this collection: Plain Magic, Testing, Time of Proving, Huntress, Mimic, Student of Ostriches, Elder Brother, The Hidden Girl and The Dragon's Tale.
Two new stories mentioned by Tamora Pierce are Lost, featuring a Tusaine girl, and Nawat.
You can read the full post with details to the stories on Tamora Pierce's livejournal.