Just wanted to pass on the update we made on the site about this:

Regarding SLI Support
We confirmed that if you have installed the “GeForce 320.49 Driver Beta” graphic driver from NVIDIA®, FINAL FANTASY XIV: A Realm Reborn will show up as a customizable game (NVIDIA Control Panel > 3D Settings > Manage 3D Settings). However, please note that we have not yet made the necessary adjustments on the program side to make the game compatible with SLI. Please be patient as we plan to have this ready by the official launch.

We apologize for any inconvenience this may cause and thank you for your understanding.