Of course, if you've been sticking to Android for a while, you understand that despite this official confirmation, the actual roll out of 4.3 may very well be months from now. It is because of this, that Sony's affirmation that an Android 4.2 update is “well underway” is still relevant. Early August is the ballpark the Tokyo-based company is targeting, with both the Xperia ZR and the Xperia Tablet Z next in line to get the now outdated update.
Sony also blogged about the possibility of leapfrogging 4.2. altogether in favor of 4.3 for some older devices. Again, timing and exactly which devices will get this treatment is unknown, but the company has promised to keep us up to date.
source: Sony Mobile Blog