Firmware update 2.0v specifically adds support for the LA-EA2 [$333.05] translucent mirror Lens Mount Adapter
In these cases, the new firmware provides compatibility with the recently launched LA-EA2 translucent mirror Lens Mount Adapter. Prior to this firmware update, the LA-EA2 only worked with the αNEX-5N , NEX-7 and NEX-VG20. We know owners of the previous models were eagerly asking for compatibility to enjoy phase detect autofocus when using one of Sony’s A-mount lenses.I can't find what it does for the NEX-FS100U (whether this adds the international frame rate support they were promising, though I doubt it) but it does add the focus peaking feature to the NEX-VG10 and the other NEX still cameras. There don't appear to be any other changes.
αNEX Cameras:New Firmware Enables Translucent Mirror Adapter Compatibility | Sony