Android KitKat firmware was recently certified for both the Xperia Z1s for T-Mobile US and the Xperia T2 Ultra. Now newer KitKat firmware for both handsets have been certified by the PTCRB website.
For the Xperia T2 Ultra (D5303) we see a very small bump in build number from version 19.1.A.0.473 to 19.1.A.0.474. For the Xperia Z1s (C6916) the build number has moved from 14.4.B.0.20 to 14.4.B.0.37. Sony is likely refining the KitKat updates before release, so we ‘ll keep you posted if/when these updates start to roll.