I've the same decision to make, and I daresay it might be tougher than yours. You've only been playing for three years, and although I haven't heard you, I could guess you aren't nearly at the same level as many others your age who want to go into piano. If you decide to go into piano, you have to start NOW. You've gotta practice consistently at least 3 hours a day, probably more to make up for lost time. And even if you practice like mad for a full year, although you will improve, you will still not surpass many other aspiring piano students in all likelihood.
Now, if you choose the computer route, there's more than just programming games. Much as jobs are outsourced to India, we do need software engineers in this country to deal with site-specific problems. Networking is very important, although networking jobs tend not to be particularly stable. You could get a job in the government, that's probably the most stability you'll get as a computer person. You could also go into Computational <something> (like computational biology, computational mathematics, etc). Computational science is a very big field, and it's growing rapidly. Computer modelling is extremely important for just about any complex/expensive experiment.
I've chosen to double major in Mathematics and Physics, but I'll also continue piano seriously. In music, it is not as imperitive to have a degree at all if you want to perform, whereas for any non-piano job, you'll want a solid degree. Math and physics is very broad - I could go into engineering with that, or physics, or mathematics, or biophysics, or physical chemistry, or even business in the technology sector. But if I choose to go into piano as a career, I just need to be good enough to win a few competitions, start getting concerts, get an agent, etc etc. None of that even requires a musical degree. Just about the only thing I probably wouldn't be able to do (relating to music) is teach music at a university.
It's a hellish decision to make, but I think the right way for you to go would be the computer path. But as you said, it's your decision in the end.