In particular he referenced “Sony/D6603/D6603:5.0/23.1.X.X.XXX“. This shows that the firmware build number for Xperia Z3 devices will move from 23.0.1.X.X.XX (Android 4.4.4 KitKat) to 23.1.X.X.XXX (Android 5.0 Lollipop). We’ll bring you any other details as soon as we have them.
Update: Looks like one of the initial Android Lollipop test versions for the Xperia Z3 (D6603) has build number 23.1.A.0.75. [Thanks Ben!]
Update 2: Here’s another one for the Xperia Z3 (D6603): Build 23.1.A.0.99 [Thanks Aaron!]
Updated 3: …and another one. This time it is for the Xperia Z3 Tablet Compact with build number 23.1.A.0.131.