Apparently Sony has been working on Android 4.3 Jelly Bean firmware
update and it will soon begin rolling out. The first country to get it
should be France as the SFR carrier has already approved the ROM
recently.
Vodafone Australia has also shared it is testing the new firmware on its
Xperia M version and if everything goes without hiccups, the Android
4.3 Jelly Bean for the Australian Xperia M should be out soon too.
So, Sony seems to be finished developing the update and hopefully it
will reach all Xperia M units around the globe in the next couple of
weeks.
According to the SFR changelog the new update will bring your Xperia M Android 4.3 Jelly Bean, faster UI, updated multimedia apps (Walkman, Album, Movies), Xperia Themes and better bookmark management in Chrome. There is no word if the Xperia M will be getting the KitKat treatment later this year as its Xperia M2 successor.