Probably more like three years. You audition during your junior year or high school, or maybe early your senior year but there's not a lot of time to switch things by then.
Check audition requirements from several places if you do audition. Or even if not. It's a good goal. You'll see the same pattern at different places.
You're a freshman in high school, so you're probably not out touring and performing. Probably not a performer then.... Too late. If you were, you'd be doing it by now and wouldn't wonder or ask. Short of performance, there's teaching (which nearly all performers do any way). For that, you're probably shooting for independent teaching, being a professor, or music education. Professor means getting a doctorate in performance/pedagogy and still kicking butt with competitions and performance. Music ed is a very different direction -- public (or private) school teaching in general music, choir, orchestra, or band. Piano skills are great, but polished performance skills don't mean a lot there. And you need other skills well outside piano for music ed.
There are other directions. Piano performance is probably too late, but conducting or composing on a world-class level is still possible. And there are other niche areas, like music theory.
Ah, next year. I glanced over it too fast. So yes, about 3.5-4.5 years. So 8th grade? Nice time to decide your career from what I've heard. I would pick a direction and go all out all that. If it's piano performance, it's that. I wouldn't split it with other things (no one on either side of the split will think you're serious about there area, esp. when they have plenty of other people who are going all out for their area). Performance, ed, whatever, but that as the goal. If you're focus is that, then maybe piano as a secondary focus, but don't expect to be that great/competitive at it. For performance you're competing against people who have been doing that as their sole focus their entire life.
The are other areas for "performance" though. Accompanying is a big one. Accompanying + teaching... People make a living doing that.