I started learning piano since 6. I guess I practiced only an hour a day back then. I won in some competitions, and did some performances every year. But around 3 years ago, when I was playing in a competition, I suddenly forgot everything.Obviously, I lost... Plus, afterwards I immigrated to another country. I then quit piano for 2 years. I only played once in a while during that 2 years. After a lot of stuff happened in my life, I found that music is the one who gives me power. It is really what I want to do. I started to have piano classes half a year ago, and started to practice like 5 hours during weekdays; 8 hours during weekend. But obviously, there are a lot of techniques that I need to pick up and work on. That I need to start from non arct level pieces right now. And I am stuck on how to play without tense and how to play with a really good crystal-like tone. I really want to become a pianist. But I am already 16. I stopped playing piano when I was 13 to 15. I am afraid it is too late for me.
I really need some suggestions. Plus I have to go to piano performance degree audition next year!! I am afraid that I am running out of time 
Let me tell you my story in a nutshell because it strangely parallels yours...
Age 7 - 11 Took lessons from a pretty good teacher. I was labeled as 'gifted' for piano. However, unlike you, I did NOT practice much at all. I could easily meet lesson requirements with a half hour of practice just before my lesson.
Age 12 - 17 No lessons. However, I fell in love with Rick Wakeman and Keith Emerson and taught myself all kinds of progressive rock stuff (it really did work my fingers pretty well). I also learned a couple of Chopin Polonaises during this time because I had grown up listening to them (A Major and Ab Major).
Age 18 - Went back to my early teacher for advice on audition pieces for the piano program at Georgia State University (had a pretty good program at the time). Picked up a Bach Invention and something by Shostakovich to go along with the Chopin Ab Polonaise. The audition was pretty bad. I was not a polished player by any stretch, but the jury saw potential and let me in on 'probation'. Probation was dropped at the end of the first quarter and I was fully in the piano performance program.
Age 20 - Performed full 1 hour recital - Beethoven Opus 22, Chopin Scherzo #3, Ginastera Piano Sonata
Age 21 - Performed second 1 hour recital - Bach Italian Concerto, 3 Debussy Preludes, Chopin Gm Ballade, Beethoven Opus 32 Eb Piano Sonata. During my recital jury, John Schneider (then the music critic for the Atlanta Journal) told me I could do whatever I wanted to with regards to piano. Strangely, this was the 'beginning of the end'.
Age 22 - Added Beethoven Cm Piano Concerto to repertoire and with the Ballade and Ginastera Sonata, won the state-wide Georgia Music Teacher's Piano Competition. Failed to advance in the southeast finals. Played the Gm Ballade at a master class with John Perry. After I played, Perry stated 'I have nothing to say...' then proceeded to say a few things anyway. He wanted me as a student at the Aspen Music Festival. I got mononucleosis and could not attend.
Age 23 - Now starting to doubt my willingness to really get into the REAL world of piano performance - I start to have second thoughts about the whole thing. For my Senior Recital, I cobble together the strength and resolve to learn Mozart K570 (Bb Sonate - nice sonata), Brahms Bm Rhapsody, Prokofiev Piano Sonata 2 in Dm and Lizst's Mephisto Waltz (played like a bat out of hell...). Also try to learn the Schumann Am Piano Concerto, but my mind is for some reason NOT wanting to learn it...
Upon graduation, I take about 2 years off completely since I did not want to have my piano in my apartment. Finally get it back and play for the fun of it.
The next 30 years are playing for my own enjoyment, but not really doing anything other than sight reading pieces. I learn and polish nothing at all. Now I am practicing once again at age 58.
So, to answer your question, it is possible to go from where you are now to professional status IF you have more willingness to do so than I did. I do not regret anything I did. Whether I play or not, music has enriched my life and the life of my family. If you are talented and are ready to start putting in 3-4 hours of steady work per day, you can get there. I did that for 4 years and was on edge of pushing through to being a very strong player. I did not have the temperament to finish the process, however.
For those that might think I am bragging about my youth... I am 58 years old now. I get to do that from time to time as long as what I say is true... ; ]