Sony released firmware version 5.0 for the F5/55. This enabled 4K XAVC internal recording on the F5 if you purchase the CBKZ-55FX optional license key. Unfortunately the optional license key isn’t yet available and won’t be until January. The CBKZ-55FX optional license key will be installable by the end user. The CBK-55PD ProRes/ DNxHD encoder board will also be available in January but that will require you to send your camera into a Sony Authorised Service Center.
   

Here is the exact release from Sony:

FAQs

1. What is the CBKZ-55FX?
CBKZ-55FX is an optional license key that activates XAVC 4K/QFHD recording and playback, 4K SDI and 4K HDMI Output as well as simultaneous recording of XAVC 4K/QFHD, and MPEG HD in the PMW-F5.

2. When will the CBKZ-55FX be available?
The CBKZ-55FX will begin shipping in mid-Jan.

3. Is firmware version 5.0 required in order to install the CBKZ-55FX?
Yes, v5.0 firmware is required on the PMW-F5 prior to installing the license key.

4. Is the CBKZ-55FX installed by the end user or Sony Service?
The CBKZ-55FZ is installed by the end user. See FAQ #5.

5. What is the purchase/installation process of the CBKZ-55FX? The purchase process is similar to any other product.
a. The end user places an order for CBKZ-55FX with their Sony Authorized Reseller or directly with Sony.
b. Sony will ship an envelope containing a purchase key and instructions for downloading and installing the license to the Reseller (reseller order) or End user Customer (direct order).
c. Reseller will ship the envelope to their end user customer.
d. The end user must follow the instructions provided in the envelope to download/install the license key.

6. What is the difference between the CBKZ-55FX upgrade option vs the F52F55UPGKIT?
a. The F52F55UPGKIT is a hardware upgrade option that offers the same image sensor and Color Filter Array as the F55, in addition to the internal 4K and output capabilities as the CBKZ-55FX, explained above.
b. One other difference is the F52F55UPGKIT permits live 4K signal output via the CA-4000 fiber adapter, which the CBKZ-55FX does not

CBK-55PD — Apple ProRes and Avid DNxHD® encoder board for F5/F55

1. When will the CBK-55PD Codec Board be available?
The board will begin to ship in early Jan.

2. What is the purchase/installation process for the CBK-55PD Codec Board?
a. The end user places an order for CBK-55PD with their Sony Authorized Reseller or directly with Sony.
b. The Reseller or Sony will ship the Codec Board to the customer.
c. The CBK-55PD Codec Board must be installed at a Sony Service Center. End users must schedule an appointment with the Sony Service Center for the installation. This is a one way upgrade; the encoder board cannot be uninstalled.