According to the unoffical Sony Ericsson blog, SEMC Blog, Sony Ericsson are currently testing Android 2.3.4 for their latest range of Xperia devices which includes the Xperia Arc, Xperia Neo, Xperia Play and Xperia Pro. The update is expected to fix bugs (you’d hope so) and provide so cool new functionality such as a cool feature they’re calling xLOUD™, which is an audio filtering technology.
SEMC points out that the Xperia X8, Xperia X10 Mini & Mini Pro will not be subject to the update, however the Xperia X10 is being tested with Android 2.3.4 but they’re unsure whether this update will make it onto consumer devices. It would make sense for Android 2.3.4 to make it to the Xperia X10 considering Sony Ericsson already confirmed that Xperia X10 is being updated to Android 2.3.3 sometime in Q3.