Hey guys I went researching for Battlefield 4 and here is some interesting info about it. (I'm not sure if this is 100% accurate!!)
PS4/X720 720p60, 60 players in MP (the reason they are not running in 1080p is because they are focusing on 60 fps)
Single player 5-6 hours long
Better weapon modification system, battlelog 2.0, better air combat
Commander mode in multi-player
Battlefield 3 players will get "veteran weapons" unlocked
Improved personalized appearance and equipment customization
Server rental
Recording function (Please note that from what I have heard that this idea might have been "thrown out". Reason for this is because it would take up so much memory for 30min-1h game