A marginal update for the Sony Xperia SP has been certified by the PTCRB. Build number 12.1.A.1.207 appears to offer small bug-fixes over the last Xperia SP update that was released with version number 12.1.A.1.205. The new update has been certified for all three variants of the Xperia SP including C5302, C5303 and C5306. Still no sign of Android KitKat being confirmed for Xperia SP users, we will keep you posted if we hear anything definitive either way.
Thanks Antonis, Kenny, Levered, nklive and Razvan_SP!