You will be required to pay the 5.00 a month PSN online subscription to play FFXIV on the PS4.

If you want the PS4 version for Free you will no longer be able to log into the game using the PS3. However.. if you choose to buy the PS4 version you could in effect have both games signed in on the same account giving you a rare option to create MULES by sending yourself Freind Request to yourself.

It's almost worth the 40.00 price to do that.