Battlefield still has some problems here and there like rubberbanding and crashing for some people. I haven't had the game crash on me since I started playing but there's a lot of rubberbanding which gets really fucking annoying. I have to point out that I got my PS4 almost a month ago and hadn't started playing BF4 until like 2 weeks ago.
As for AC4, I have heard good things also so if you want, go for it. People say it's a lot better then AC3.
Play Outlast if you haven't already. Also, go pre-order Infamous.