The PlayStation 3 and PS Vita share the sort of relationship that the Previous Sony Portable could only dream of. Maybe the PS3 thought the PSP was the one, but now it's found something much more intimate and personal.
Vita players can play games against PS3 players. They can play games with PS3 players. They can play games on the Vita as a second player using an entirely different perspective than the PS3 player.
Ultimately I could see this relationship evolving into something akin to what Nintendo is doing with the Wii U's HD display controller. We waited too long for the PlayStation Move. Now Sony has technology in place to potentially copy Nintendo before Nintendo's new tech even hits the market! That's foresight.