I watched this video on the new PXW-X180, and the Sony rep mentions that the 300 will get the XAVC Intra update in June, 2014, and the Long GOP update in October, 2014 (at the :44 sec. mark)

Sony Professional - NAB 2014 - Introducing the new PXW-X180 - YouTube

Well spotted. Thanks for posting!

At 3:19 in the video, underneath where "SxS" is marked in white ink, it looks like they have a full sized USB3 connector (complete with the blue coloured thinggy).

Andrew