I think you said something wrong there

This shouldn't be true unless the pre-orders empty the stock everywhere.So, if you don't end up getting the Special Edition with the figurine, you won't be getting the Terminal Disk.
The special edition isn't supposed to be limited. It's just that i you pre-order the special edition from eb or gamestop, you get the figurine with it for free.
The terminal disc will always be attainable by buying a special edition, but the figurine will only be the pre-orders of it.
I refer to the pre-orders of the special edition as the limited edition. I suppose that might've brought up some confusion.
As soon as the game is out (or their stock of the figurine has run out i suppose), they'll most likely change their "Dot.Hack G.U. with Exclusive Figurine" to something along the lines of "Dot.Hack G.U. Special Edition" or "Dot.Hack G.U. with bonus disc".