I have that same dilemma and am hoping to purchase a ring with my boyfriend by the end of next month. I am afraid the ring I want with the specs I am looking at will be gone by the time I am ready to buy!
I talked to my SA and he said that if there is a price increase, it will most likely occur at the end of their fiscal year, which happens to be end of January. He wouldn't tell me how much of a price increase it will for fine jewelry/engagement rings because he said it depends on each individual piece and how well sales were for the quarter, etc. He promised to give me a heads up if an increase happens, but he says sometimes headquarters in NY just updates the system without giving any warning, so I am not putting my hopes on that.
Once prices go up, prices stay up until the assessment period at the end of the quarter/next fiscal year for them (not sure when the next one is). I'd talk to your SA on Monday and ask to make sure when that will be if you are not ready to buy until spring. My fear is, prices will keep going up, so I'm trying to buy now, versus later. Seems like sales were well this Xmas and I know prices of gold and diamonds keep rising, and I don't know how long Tiffany can hold off without raising prices soon!