Pretty sure the "Gold Saucer" is going to be in Ul'Dah. Right next to the entrance of the Pugilist guild is a NPC standing behind a booth and the area is called Platinum Mirage. If you talk to that NPC, he/she (can't remember gender of NPC) specifically talks about a casino area that you 'don't have the bankroll to be a part of yet'. I didn't play 1.0, so unless this is something different from 1.0 that hasn't been implemented into ARR yet, I'm not sure. If not, I would feel safe expecting this to be where you would enter the Casino.

Unless they expand the area of Ul'dah, this would almost certainly be instanced.

Please look forward to it!