If you had linked FFXIV version 1.0 to your SE account, you should just have to download the game and login.
You will not have to pay for the game again.
Yes, the game will come out on PS4 though you will have to buy the version of the game for PS4 again. You don't get free PS4 disks just because you previously bought the PC version.
FFXIV: Crafty Hallie, Ultros