Whether FFXIV can survive on a subscription model has nothing to do with whether it goes free-to-play. It depends on the size of the team that developed it, the persistent cost of the server infrastructure, and the size of the team that maintains it and develops new content for it.
Frankly, it will be a long time before FFXIV will be profitable for Square|Enix, no matter what its subscription base ends up being, or whether it goes F2P or not. It's an MMO that's been almost completely restarted, in addition to its initial up-front cost and ongoing server maintenance. It's also possible (maybe even likely) that FFXIV will never be profitable, and that Yoichi Wada knows this, and that 2.0 is more about saving face and repairing his company's tarnished reputation.
I believe free-to-play will result in a worsened play experience than a subscription model. Free-to-play incentivizes developers to water-down the base experience of a game in favor of the up-sold version. It creates pressure for them to contact their users as frequently as possible to try and sell them on the game's paid-for assets. This is why free-to-play games usually become pay-to-win: You've turned the game from a service to a retail outlet. It's the same difference between a fitness club and Wal*Mart. I don't want to give Square Enix an incentive to email me reminders that I haven't played recently, or to give them an incentive to make paid-for weapons of any sort better than the weapons I'll earn in-game. If you ask for the game to go free-to-play, these things will happen. That, or the quests will become for-pay, similar to Dungeons and Dragons Online. Or the player customization. Or maybe even the different zones of the world. Possibly, all of these things. Whatever it is you like most - whatever would make you pay the most - that's what Square Enix is best off barring from you until you pay real money. That's the business model you're asking them to go into. That's what you're asking them to do.
League of Legends is no exception: They operate as a retail outlet for characters and customization, with what could really only be described as a free online trial. They have almost no map or gameplay options. You find a hero you like in the random roster? Then you have to wait for them to cycle back into the roster, or you have to pay real money. And you want the latest Teemo skin? Money, money, money by the pound.
And as a game developer, myself, I tend to find the free-to-play model ethically questionable. Free-to-play games survive on what are called "whales". These are people who spend thousands - thousands - of dollars every month. I can't understand what drives these people to spend this kind of money, and I can't imagine that it represents a healthy relationship with the game. Knowing that they exist leaves me wishing never to work on a free-to-play project.
But in summation, I suppose if you'd really be happy paying nothing and doing nothing except grinding vanilla mobs in New Gridania, then I guess I can't stop you from asking for free-to-play. But please stop jumping on the free-to-play bandwagon as if it will make the game free for you without fundamentally altering your play experience. It will not.
Edit: Oh. Bother. Obviously I fell for the troll.