Bro, I know it sounds like everyone here is talking down to you, but believe me we all got the same interest in mind.
I also understand you not wanting to wait another 4 years for a streetbike, especially if you are lucky enough to afford one at your age.
However, trying to learn two things at the same time, can easily lead to mistakes, and mistakes on bikes tend to at the very least hurt a whole lot.
Riding a sportbike on the street and riding one on the track are two totally different animals. While I'm not a dirtbike person (lack of opportunity, not desire) I suspect that trail riding and racing them are quiet different too.
So if you do get a streetbike this early, take it to the track. Its time well spent, especially if you want to end up in the racing world. Try to keep it off the street, at least for the first year. People on highways are all homocidal maniacs, and they all try to kill you. Really, some arent paying attention and dont give a damn about what happens to you, others just dont like sportbikes and think its real funny to run us over and make us crash. It doesnt register with them that someone is going to die, they look at it like swatting that annoying fly.