I'm not sure if you said you already have a piano background, or that you would have one if you majored in it.
These days, I think pursuing electronic music & recording technology is the way to go if you want to be a professional musician. A background in piano is a great start. Keep taking theory, composition and orchestration classes, but also learn how to use the complicated samplers and workstations that will let you "play" the sounds of an entire orchestra. I think as the technology changes, those skills will make you more hireable and more adaptable than being a really good pianist.
That said, I'm sure folks have told you that there are very few music jobs. The folks I know who do are full time musicians tend to be on a scale between:
A) People who make the music they want to make, and make ends meet by giving music lessons, etc, and wind up making about the same amount of money as if they worked at McDonalds full time.
B) People who make the music they don't want to make - for example, they make commercial jingles or music for educational software. Some of these assignments take a rather uncreative approach. One friend of mine who makes commercial jingles was asked to record 30 versions of a BB King song, all trying to sound as much as possible as the original recordings by different blues musicians, because the company didn't want to license the original recordings.
C) People who are honest to goodness professional musicians in the way you think: I know 2. In both cases, they were able to be professional musicians only for the 3-5 years that their bands were really popular. Then they had to supplement their income with music-related jobs.
D) Professional Musicians through Grantwriting: Again, I personally know 2, and am acquainted with a 3rd. All 3 spend as much or more time either applying for grants, high-paying residencies and performance opportunities as they do making music. That's not bad - it's just what it takes. The good news is they get to make the music they want to make. One caveat here is that they are all dream candidates for grants organizations - they look great on pamphlets that say "we gave our grant to this person". Two are hip-looking, beautiful ladies, and the third is a hip-looking, very handsome man. They are very talented at their music too - appearance isn't anything, but I know lots of talented, hard-working folks who don't get grants.
Another thing to consider is music-related jobs. I know a few people who are employed full time running the recording studio that records voice talent for videogames and software. Others work for music services like Pandora.
I think it's kind of unfair that the education system expects you to know what you want to do with the rest of your life before the age of 20. About half the adults I know wound up in careers that are unrelated to what their college major was.
I for one really enjoy having a day job that is not related to music. I switched majors from music to psychology in college, and now work in an office. I discovered in my 30s that I have real talents that are not at all music-related (or psychology related), and that I honestly like the nature of the work I do. This leaves my musical mind "fresh" when I want to play the kind of music I want to play, and I don't struggle for money as much as many of my professional musician friends.
http://www.youtube.com/user/ribosomemattGmail <firstname.lastname@example.org> was like:
So I'm at the part of my life to choose what I want to do in the future (Junior year highschool). I feel torn by this decision especially considering that I'm highly indecisive on a daily basis... I kinda want to major in some field of piano music, but I don't want to have to end my hobby/goal/love for electronic music. However without my piano background I probably would have no musical knowledge to fuel my electronic music and also wouldn't have known the joys of the emotional roller-coaster music brings :p.
Basically I'm asking (particularly anyone who has been in this position) What should I do? It feels like the end of the world for me right now yet its barely the beginning :/