Sony is firing off Jelly Bean updates for a few handsets this week, starting with the Xperia T and V, with the TX to receive its Android 4.1 update in March. This conforms with the statement Sony issued previously about updates to these devices, back in December. Here's what Sony says is contained in the update:
Way back in December 2011, Sony began releasing 'alpha' developer ROMs for some of its phones being upgraded to Android 4.0. Then it released beta ROMs that did slightly more stuff. Now it's done the same with Android 4.1 for the Xperia T.
These ROMs are developer-facing in every sense of the word, though, and aren't intended as a way for power users to get early access to the next version of Android.