If you're flexible with dates and where your room assignment is, I would wait. We were thinking about cruising 10/5 eastern on Fantasy this year. The price for inside was $2900 and lowest cat veranda was $3200 for 2a 1c. We ended up booking for Nov on a Military rate instead. Out of curiosity, I kept watching that 10/5 cruise. I noticed in the middle of Sept there was a IGT rate and it would have been $1790 for the three of us and a VGT rate at $1950.
Same thing happened with our Fantasy cruise in fall of 2012. We paid full price. After the PIF time....some great GT rates and other discounts became available.
If there is a specific cruise I'm looking at, I stalk it. Figure out when the PIF date is and check availability. If all categories appear to be available, give it a week or two and continue to check daily. If they still have a lot available, chances are, there will be a GT rate that will show up. I check rates frequently and this has been what I've found with any cruise that appears to not be selling all categories.