The Last of Us creators, Naughty Dog, recently held an AMA (Ask Me Anything) on Reddit, where several people asked Neil Druckmann and Bruce Straley about the future of Jak & Daxter. In reply to a quest about Jak 4, Neil said:
"No plans. We gave it a shot at the beginning of the project and couldn't make it work for ourselves."
Another user asked again later, to which Neil replied:
"We tried and failed. :( Maybe in the future we'll try again."
So it looks like Naughty Dog were working on bringing the platformer back at one point, but couldn't get further than the concept. On the upside, we got The Last of Us instead, which is one of the best, if not THE best, new IPs this generation.