We know that Sony is continuing to use two model naming schemes side-by-side. The first is the new CXXXX naming structure for handsets released in 2013, whilst that used for handsets in China continues to be the old structure with S/M/L denoting small/medium/large handsets. So it seems pretty much a given that this handset is being considered for China, but we don’t know if it will see a release outside the region at this stage.
We have no idea if this handset is a prototype or whether it will see production. However, we’re already seeing a growing number of Xperia handsets for Sony’s 2013 smartphone portfolio. We’ll keep you posted if we do hear more on the Sony S39h.