You are right. You should get nearer your sustainable goal weight before having zeltiq. I include the word "sustainable" because there is often a difference between what we want to weigh, and what our bodies will allow us to weigh. It is important to be realistic.
Zeltiq is meant for those stubborn pockets of diet and exercise resistant fat. Zeltiq may actually work better when you are at your goal weight. The reason it that weight gain stretches our skin. As we lose weight, our skin becomes a little more lax. The Zeltiq probe may be better able to suck in that slightly more lax skin, thereby allowing the probe to treat more fat cells.
In addition, once you are at your goal weight, your consulting physician will be able to better assess the elasticity of your skin. If your skin is too saggy (this is usually the case after too much weight loss or weight loss that happens too quickly - eg after pregnancy), then you may get a better result from a procedure that removes fat AND skin.
Good luck!