PlayStation 3 version: Why Bother?
Because the PS4 hasn't even been announced yet(yes yes, we know "it's coming", but there hasn't been even a sliver of anything official other than that), and given that Sony has said time and time again that they want the PS3 to have at least a 10-year life span, we probably won't be seeing said next-gen console in a bit, Microsoft be damned in this scenario.

As others have said, the PS3 currently has a global install rate of about 70 million or so, whereas again, the PS4 would take some traction to get anywhere. True, we can easily say that 70 million PS3 users doesn't mean they'll all play FFXIV, but if even .05% does, that's still a good 4.5 million subscribers. Many people I'm aware of have been waiting on the PS3 version for a LONG time, so there's definitely at least some audience.