If you were waiting for Sony to finally decide the fate of Xperia T, TX or Xperia V smartphones, the company has released the verdict. It now clearly states on the product support pages for these smartphones that Android 4.3 is the final Android release for them, which means no Android 4.4 update.
As Sony Xperia T and TX are almost two-years old and Xperia V is around 21-months old, this move is not surprising. The Android manufacturers typically provide major Android updates for up to 18 months or sometime not even that long.
Android 4.3 in itself is not a very old Android version, so you won’t be missing much. If you really want Android 4.4 on your Xperia smartphones, you can always go for the unofficial ways as there are a decent number of KitKat custom ROMs for these smartphones. Check out XDA-Developers for the custom ROMs, however if you are not experienced in rooting/ modding stuff, you should probably stick to Android 4.3.