It's not too late to start gymnastics or persue any dream you have but you have to be realistic. Olympics - only 6 girls go and usually they have been doing gymnastics since they could walk, spend 40 hours a week or more in the gym, parents are in debt up to their eyeballs to pay for the coaching, homeschooling, and everything else that goes with it.
Every girl who does gymnastics has the Olympic dream and anything could happen but being a realist you have a better chance of looking to be on your High School team if they have one and maybe making a college team and getting a scholarship. That is my DD's "Olympic Dream" Scholarship money and having fun doing it.
In the end it should be about loving the sport, working hard and having a ton of fun while doing it. If you have that who know what will come your way. Go for it and just have fun