If you loved Knack, and would like a sequel, there might be some hope, if a listing on the Linkedin profile of Animator Mindy Liang, working at Taiwan-based developer XPEC (the same company that is working on assets for Final Fantasy XV)
The listing has been recently removed, but nothing really disappears on the internet:
Apparently, Liang started working on the game in May 2015, as Sony presumably outsourced assets to XPEC, pretty much like Square Enix is doing for Final Fantasy XV.
Of course, this shouldn’t be considered as a full-fledged confirmation of the existence of the game, and we should keep in mind that Sony made no official announcement. That said, CEO Andrew House did mention that Sony intends to “cherish” the character, so a new game isn’t really that unlikely.