I personally don't think it's realistic if you are doing it in a healthy manner. It's a high set goal which is awesome and great but as long as people have said if you don't hit it in tha amount of time you don't get all upset about it and are happy enough with your progress to start. I lost 20 pounds in 3 months and was at the same weight for months after that, but was still shrinking. It's not about how much weight you can lose in a little bit of time, it's not a diet it's a life style change. You can drop all that weight but if you plan on going back to your old habits why even bother, you'll gain it plus some afterward.
Be smart about it, research, come on the fourms for support and if you don't reach your goal be happy with the progress you made so far and continue on with your journey.