Yoshida has leaked out all of the exciting possibilities with what is termed "Couch Co-Op"
Recently there was a demonstration by Sony when they were playing the PS4 and Vita with Remote Play at the same time using the title Knack with what is termed 'Couch Co-op." As demonstrated in the video below, there are tons of exciting possibilities that can be used when one player is using the Vita via remote play along with another playing using the PS4 during co-op.
A person tweeted to Yoshida if this was limited only to Knack or if it could work on Lego Marvels. Yoshida replied on Twitter that it will work with any game that has 'Couch Co-op" which is pretty cool. Check out the twitter here along with the video as well.