So, I'm bouncing between Battlefield 4 and Killzone if I decide to buy a disc game once I finally find a goddamned PS4 to buy. So here's the deal if say... I bought Battlefield 4 and started playing multplayer would all of my rank and whatnot automatically carry over to the PS4 version? Cause if I finally decide BF4 I figure I might as well buy the PS3 version and start playing now then just transfer everything over to PS4 once I get it.

From what I've read, it crosses over from the "same" platform version. Ex: PS3 to PS4.

Yep this. If you do the upgrade all your stats and DLC's transfer including premium.

Yes - it does. Here is some more info.

http://www.battlefield.com/battlefield-4/playstation-4-upgrade

Stats, unocks, and Premium membership carry over.