If you are not Trolling: Think of A Realm Reborn as a whole new game. Maybe you can forget FFXIV 1.0 ever existed and think of this as the true FFXIV. As far as I can tell it will be a whole new game. Almost everything will be new or replaced/updated. The only thing that comes from 1.0 is our personal data, it would seem. I'm looking at it as a new game that I just bought. Of course I get to take my character data with me so I don' have to grind a few jobs, so that's cool. So, I would think they hope to have a good lifespan, matching our beloved FFXI in replay value.
If you are Trolling: I think when they shut off the servers and game itself (1.0), you know when no one can play anymore while they "transfer" all the data to 2.0. That's when they will shut down the servers all together and forever, playing the biggest trick on all us FFXIV 2.0 hopefuls. They were trying to get a few more dollars before they killed it. It worked too, Legacy got a few thousand people at least to sign on for 90days, and then they kept people from leaving. I say good work SE, that's the way to rob us blind.