Before moving on to Uncharted and The Last of Us, Naughty Dog considered the idea of rebooting the Jak and Daxter franchise with a more realistic approach, in a PS3 title tentatively named Jak 4 or Jak and Daxter 4.
The project did not pan out, but the concept art studio Scribble Pad Studios (that works for many clients in the industry, including Naughty Dog, Sony, Activision, EA and many more), published a few of the original concept designs created for the game on its ArtStation page.
They definitely show a more realistic design for Jak, and the environments (by Scribble Pad Studios Creative Director James Paick, who worked at Naughty Dog as a Concept Artist from 2008 to 2010) are absolutely lovely. Some of the designs appeared in the recently published The Art of Naughty Dog, but finally we get to see them direct feed, in their full glory.
[Thanks for the tip: Tyler Casilio]