Can't say this is a big surprise, 2017 F150 will get this transmission too, I have only read good things about the trans from the ZL1, interested to see how the Mustang will preform with 10 gears!
http://www.autoblog.com/2016/06/20/10-speed-automatic-rumor-2018-ford-mustang/
http://www.autoblog.com/2016/06/20/10-speed-automatic-rumor-2018-ford-mustang/