While we haven’t heard much about Skype for Business mobile UI it would be expected that the UI will get refreshed as well. @NovoaGO has posted a picture of an updated Lync/Skype for Business mobile app with what appears to be a new UI.
Q-When will the Skype for Business mobile client update be released?
A-“Skype for Business mobile application will available…in the coming months” (redmondmag.com) click here
UPDATE: According to Windows Central the Windows Phone Skype for Business client will be updated May 15: Click Here
Note: We have not seen this update on our Windows Phone or Android devices…yet.