It would seem Sony wasn't too keen to sign up for this service, so you won't be seeing Xbox live on your PS4 any time soon.
Just how keen is MS to have PSN on Xbox? I'll wait till MS posts up "Xbox Live coming to other platforms, while we're also welcoming PSN & other services onto Xbox if they so desire."
I'm still hating on cross-platform play, I didn't mind the odd game like DCUO, FF14, WarThunder, Rocket League in a few other games like Sony supported way before MS, but gamers are asking for all games in that would lead me to ditch MP gaming on console...