Join Date:Joined: Jun 2013
It looks as though around 20% of the software variants available for the XSP (including generic / sim-free ones) are still 4.1 based. Unfortunately both yours and mine are amongst them.
If you don't want to wait for the update to become available officially you can always download one of the 4.3 FTF's that are available and flash it, though you will have to wipe your phone if you decided to do this, whereas the official update should just 'upgrade' what you have already. Although, that said, a number of people have reported that the 4.3 update works best when you reset your phone back to factory...