I'm not sure why both Sony and Microsoft didn't support 4K out of the box with their latest-generation consoles as 4K was already becoming mainstream when these products launched. That being said, Sony alone is prepping an in-between launch update for their PS4. It's essentially a PS4.5 and it will support 4K. Essentially, all other software and hardware capabilities will stay the same, but it will have a faster GPU and more robust video output options to support fast 4K video.
The beefier specs come with a mandate from Sony to developers: Games running on the NEO need to "meet or exceed" the frame rate of the game when it ran on the standard PS4 hardware. Pricing is unknown, but the possibility of this releasing for $400 while the base model finally gets a price cut to match the Xbox One doesn't seem too far fetched.