President of Sony's Worldwide Studios Shuhei Yoshida has confirmed that the PlayStation Vita will not be able to be used as a second controller for the PlayStation 4 by default.
When asked on Twitter about whether or not the Vita could be used a second PS4 controller, Yoshida replied, "In a normal sense, no. Unless a game is specifically programmed to allow such use of PS Vita."
This comes across as odd news since every PS4 game must support PS Vita remote-play so the controls for any PS4 title would be mapped to the Vita. Now it's up to the developer to add the ability to use the Vita as an additional controller.