I don't expect FFXIV to go anywhere anytime soon. We've likely go at least two more expansion, potentially more - which would be at least another 4 years worth of content. Even when the game ceases to be updated, FFXI is proof enough that the plug won't be pulled on FFXIV for quite some time.

Now, personally, I'd quite like to see a new Final Fantasy MMO at some point. I'm in no rush, though - and I hope that if one is made it's more 'high fantasy' and learns from the mistakes FFXIV made in regards to player housing and character customisation.