What to do about Bridesmaid Dress -- Alfred Angelo

I will be a bridesmaid in my friend's wedding on march 14, 2009. She wants us to wear Alfred Angelo bridesmaid dresses, which mean I need to order soon, since they tell you it takes 16 weeks to come in. The problem is I am trying to get healthier and have been losing weight and plan on hopefully losing at least another 20-40 pounds before her wedding. So what would you do about ordering a dress? Obviously if I order the size I am now, if I continue to lose the weight I want, it would be HUGE by the time it came and needed to be severely altered. But I can't wait too long to order or it won't be in in time to alter before the wedding. Anyone been in a similar situation and have any advice on what to do??