A new firmware build has been certified by the PTCRB for the Xperia Z2 (D6502, D6503) and Xperia Z2 Tablet (SGP521, SGP541). Build number 17.1.A.2.49 looks to be an incremental update over the previous Android 4.4.2 KitKat build (17.1.A.2.36).
Whilst the Xperia Z2 is largely still waiting to be released, the Xperia Z2 Tablet is already shipping. So we would expect this new update to hit the Z2 Tablet in the coming weeks.
Thanks Ben and Rimas!