The easy answer is yes. A drop of 2 seconds over 50 metres freestyle is very possible for a 17 year boy. Your body will be continuing to grow and your increased strength and power will assist you to swim faster than you ever have before.
You will need to work with your coach to ensure your training program gives you the best opportunity
Your ability to improve will depend on continually improving your technique, the continued development of upper body strength and your ability to transfer any strength gains into the pool when swimming freestyle.
With your training, it is important to continue the development of your aerobic fitness as most sprinters will only take between 1 and 5 breaths in a 50m freestyle.
You also need to work on your upper body strength by doing some pull work. I have found using a band around my feet and sprinting for 15 to 25 metres as a useful way to improve this.
Train hard and let me know how you go. You can also secure this great eBook written by Australian Olympic Coach (2004 & 2012) Leigh Nugent Improve Your 50m Freestyle.
The Swimming Expert