Few days ago Sony revealed its Android 4.4 KitKat and Android 4.3 Jelly Bean update plans, where few new devices were missing from the list. If Sony's support pages is any indication, then Sony will be updating the Xperia SP to KitKat in the near future. The pages also revealed the list of devices who might or might not get the KitKat update, but will surely get Android 4.3 on it.
According to Sony support website, the Xperia T, Xperia TX, Xperia V and the Xperia ZR Android 4.4 KitKat update is under investigation, whereas the Xperia SP, Xperia Z1, Xperia Z Ultra, Xperia Tablet Z, Xperia Z and the Xperia ZL will be getting the KitKat update.
The exact release date is not yet revealed, but Sony notes that all the above stated devices will be getting the Android 4.3 Jelly Bean update before the year end.
Source - Sony Support
Via - XperiaBlog
To be updated...