I have lost close to 100lbs and have no loose skin.
Like shiftedshapes said if you are young it will probably not even be an issue. If you are mega concerned here are some things you can do: Be sure to get all essential nutrients so your skin has the needed nutrients to rebuild collagen and elastin, do not lose weight too fast, keep the skin hydrated with a good quality moisturiser twice a day, keep hydrated internally and keep your intake of quality fats high.
Your skin will probably be fine though, mine is, don't panic