I Alpha tested the game and it required a beefy video card but now the beta requirements have gone a bit lower so it would be wise to wait until full optimization of the game is complete (by the way, the graphics in FFXIV are awesome)
If you wait, it may give you a little more time to save $$$ to get a better card than the 5770.
when you get your new rig, what will be the specs of that? Most notably, what video card will you be getting?
As for now, your rig is definitely capable of playing FFXIV, you just won't be able to max it out.
Here are the new minimum system requirements:
OS Windows® XP SP3 *1
Windows Vista® 32-bit / 64-bit SP2 *2
Windows® 7 32-bit / 64-bit *2
CPU Intel Core 2 Duo (2.0 GHz)
AMD Athlon X2 (2.0 GHz)
RAM Windows XP: 1.5 GB
Windows Vista / Windows 7: 2 GB
Hard Disk Space Installing: 15 GB
Downloading: 12 GB on the drive containing the My Documents folder *3
Graphics NVIDIA® GeForce® 9600 or higher VRAM 512 MB
Radeon™ HD 2900 or higher VRAM 512 MB
Sound DirectSound® compatible (DirectX® 9.0)
Internet Connection Broadband (constant connection)
Monitor Resolution 1280 x 720 or higher; 32-bit
DirectX DirectX 9.0c
Other Mouse, Keyboard, Gamepad *4
I know the Alpha system requirements called for an 8800GT 512 meg or better and the dual cores had to be 2.4GHz or better
well, i7's are decent overclockers so don't worry too much about the extreme editions as they are a waste of $$$ I would say the i7 9xx would be the best choice, most likely the i7 950 as the price will go down from $564 to $295.
If i were you, i would not upgrade from the 8800GT to the 5770 as the upgrade would be nice but you might be better served to save the $$$ and get 2 5870's
Another option is to get a 5850 instead of the 5770, thet way, you can corssfire it with another 5850 or 5870 when you get your new Rig in March.