"The result of all of these fancy numbers is a PS4 that can output games at 4K"
No, no it can't. $1000 GPUs struggle to push modern games 4K at decent frame rates, this GPU won't get anywhere close. Likely this new GPU will push 1080p/60FPS where the original PS4 was often limited to 900p/30FPS.
They could indeed 'enable' 4k, for the console OS and Games, and technically the PS4.5 could 'run' games at 4k... but they wouldn't run very well... I think this Console Update is more for VR as they need the extra horse power to power their new headset.
From the looks of it the PS4.5 will have a big GPU upgrade to a R9 480 equivalent. The R9 480 is expected to do about as well as the R9 390. So, 1080p @60fps? Check. 1440@playable FPS? Yes. VR? Also yes. But 4K? I very much doubt it.