The decoding software and hardware are irrelevant if the HDMI chip can't handle 4k 60fps, that's why I want to know about that in particular. You say the exposed pins on the chip are significant, but to my inexperienced eyes it looks just like the Panasonic hdmi chip used in the PS3 Slim, but with a slightly different number. Is there a difference?
Yes several related to the industry.
The rules for DRM have tightened:
1) You are now not allowed to have exposed Pins unless the media is encrypted
2) Playready 2 , Playready in the app its self will soon not be allowed on the PS3.
3) Playready 2.5 and 3 require a TEE where the PS3 supports porting kit 2.5 and the PS4 supports porting kit 3. In both cases no media is allowed outside the TEE unless it's encrypted. All hardware is evaluated and given a rating and that rating determines how secure the platform and depending on that rating, media of lower or higher resolution may be allowed. Some is predetermined some is determined by the Playready program it's-self. The HDMI 1.4 port in the PS3 degrades the Playready security rating to 1080P and the exposed pins even lower with the new standards. The PS3 could implement watermarking which may up the security rating high enough to allow 1080P on the PS3 with the new standards. HDMI 1.4 has a broken/hacked DRM so I don't know how Grandfathered it will be and what will be allowed for it.
EDIT: HDMI 2 has a feature where it can be served over Ethernet as a HDCP 2 encrypted and I think compressed stream. With a Firmware update the PS3 could support this.
The PS3 as a 2.5 encrypts the memory and OS and has a Virtual protected environment as a TEE
The PS4 has a Trustzone processor in Southbridge with it's own 256 MB of memory. 256MB is too large for just a southbridge or for background tasks which was one of the confirming points I predicted before the hardware breakdown.
Edit: Sony in letters to the EU power board was complaining that the Media Power mode would require a Apple TV like SoC in the Game Console. Semiaccurate was stating in 2012 that the PS4 would come as two chips, the XB1 as one with the AMD/Microsoft project name Kryptos (leaked by Sweetvar123) which is the name of the Statue outside the CIA in Langley. Kryptos was referring to hidden DRM/Cryptology which is the Media Trustzone SoC inside the AMD APU. To meet the EU media power modes the XB1 has to use DDR3 memory which then required the large cache memory for games and that reduced the size of the GPU they could have. Sony moved the ARM block out of the APU into it's own "Apple TV Like" SoC with it's own DDR3 memory so they could use DDR3 for a Media mode and GDDR5 for Games on the APU. If HBM were available this wouldn't have been needed.
What this tells us is that Media and DRM are a major design criteria for both consoles contrary to what many think of the PS4's Game only thrust so far. But to this point Sony has not published the APIs to companies like Netflix to use the Southbridge embedded DRM and player. I believe they will so so when HTML5 <video> MSE EME makes it into the PS4 Browser and that enables ooVoo also.