In response to a question asking if the PS Vita "Can be used as a second controller on the PS4," Yoshida responded, "In a normal sense, no. Unless a game is specifically programmed to allow such use of PS Vita."
@InsideEddie Hey BRO! In a normal sense, no. Unless a game is specifically programmed to allow such use of PS Vita.— Shuhei Yoshida (@yosp) July 26, 2013
In May, Yoshida confirmed a report saying that Remote Play support would be mandated for all PS4 games. That feature, which debuted on PlayStation 3, allows games to be streamed to a PS Vita from a PlayStation console via Wi-Fi. At the event in which Sony unveiled the PS4 in February, it also announced a goal to make all PS4 games available on PS Vita.