As reported earlier, Sony has officially revealed the list of Xperia devices which will receive the Android 4.3 Jelly Bean and newly announced, Android 4.4 KitKat update. Sony has decided to skip Android 4.2 update for range of Xperia devices, and has opted to go directly to Android 4.3. The company has also listed out the first raft of Xperia devices which will receive Android 4.4 KitKat update.

Sony has also revealed the first batch of Xperia device which will receive KitKat in the near future. Exact dates/timing is not yet given. For now, the Xperia Z1, Xperia Z, Xperia ZL, Xperia Z Ultra and the Xperia Tablet Z will get the latest 4.4 KitKat update.
As mentioned already, Sony notes in the blog post that this is the first raft of Xperia devices which will receive the Android 4.4 update, so we may except to see more Xperia smartphones getting the Android 4.4 update, as Google has designed KitKat to run smoothly on devices with as low as 512MB RAM.
Source - Sony Mobile Blog
Via - GSMArena