The white UI that purportedly is coming with Android 4.3 for the Sony Xperia ZL does make sense considering that it matches the UI for Android 4.2.2 seen with the flagship Sony Xperia Z1. It is believed that the Z1's interface is coming, not only to the Xperia ZL, but also to the Sony Xperia Z, Sony Xperia ZR and Sony Xperia Tablet Z.
Speculation is that the Japanese OEM will start rolling out the Android 4.3 update in the middle of this month. In the meantime, you can check out some screenshots below.
Thanks, Anonymous Tipster!
source: bbs.gfan.com (translated) via XperiaGuide