Cruise pricing isn't an exact science, and you're always taking a risk by waiting for a possible price drop. The cruise lines put the best prices out when the cruise 1st goes on sale. Then, they will adjust the prices as it gets closer to the sail date based on what inventory is left and how well it is selling. The cruise lines like to have at least half of their cabin inventory sold about 10 - 12 months prior to the sail date. They do this to give those that booked early the best price and reward them for their early booking. As the sail date gets closer, they may drop the prices of certain catagories if those catagory cabins are not selling at the rate they need to be. The cruise lines like their ships to sail full, an empty cabin makes them no money.
There are 2 potential downfalls to waiting to book and see if prices drop; 1: If the inventory is selling as required by the cruise line, or even at a faster rate, the prices will go up, not down. 2: By waiting, when the cruise line does drop the prices, it will be for the cabins in lower catagories and not the most "desirable" cabins available. The 1 potential upside ofcourse is that you may snag a pretty good deal on a cruise. So, you have to weigh the 2 potential risks versus the 1 big potential upside for you. For your information, the best and most expensive staterooms on a ship are the ones that sell first from a ship's inventory when the sailing 1st goes on sale.
One way of alleviating this, is to book and deposit your cabin as soon as possible, and then if you see the price go down, a good TA will be able to get you the lower price by getting the difference taken off the final payment, or at least get you an onboard credit for the difference.