Extremely doubtful that they will ever drop support for the ps3 users.

How do you think you would feel if you've been playing on ps3 for a few years, and due to your luck you never got around to getting a ps4 or maybe you just preferred the Xbox one instead. What then when they tell you "sorry guys but that game you paid for and all those monthly fee's you paid were great and all, but we regret to inform you that you can no longer log in with your PS3 since we've decided it's too old."

If you honestly think that won't enrage the user base that is on the ps3 then you are quite simply not a student of human nature. Square enix isn't that stupid either. Look at FFXI and you can see that they supported the PS2 almost the entire way despite the fact it hindered the game.