I am interested in getting jaw and/or chin implants, but fear that after building more muscle/maturing a bit more my face shape may change?

Talk to surgeon. Any plastic surgery is affected by age, weight and time to varying extents. Talk to a couple of different surgeons about what you want done, what you hope to achieve and the results both long term and short term of any procedure. Go with the doc who you trust most and do some research about the procedure on your own as well.