The official Sony Mobile support page for the Xperia S has just listed the latest available software as version number 6.2.A.0.200. We understand that the 6.2.X.X.XXX release relates to the Android 4.1.2 Jelly Bean update.
The release date for this firmware is listed as 24 April, which must be a mistake but could be inferring to a 24 May release? Interestingly, the firmware build is different to the one that hit the PTCRB recently (6.2.B.0.200). Hopefully, we hope to hear soon which one is right.
Thanks Aaron and Sekhargreen!