In fact someone mentioned a while ago that Naida Cole was giving up her concert career to study medicine 
So, there. 
I wouldn't doubt it - and there's John Carmack [and a few others that attempted the X prize stuff, no doubt] for the 30+ rocket scientists [if you've never heard of him, then you've never played quake or doom]
I don't think I'll be any worse / better because I'm not 5 or 15 - bar the fact that I'll run out of time at some point. Or in other words, I wouldn't have been a concert pianist if I'd started when I was 5 either.
That said you need a piano around, otherwise an argument about opportunity could be made. But if my 6yo wanted to play the piano, there's a digital there and nothing stopping him [unless he's fussy and waiting for a decent grand] he certainly hasn't shown much interest - perhaps he will if he sees someone playing it a bit better. But I don't see much point in lessons on the basis of "he's 6 and it'd be too late if he doesn't start now" because, I think, if he was Mozart II he'd be playing. OTOH, mebbe tomorrow or next year he will and he'll reach the same standard he was ever going to, whenever he starts, bar ill health or death.
That said, you'll say it's not talent. Ok, I'll say it's like the 80%/20% rule - the first 80% is "easy" compared with the last 20% and the gulf between them is probably negligable in some respects, but unbelivably huge in others.
Most that get the 80%, I'd say nigh on all that are over a certain age, but clearly nigh on all that are below it too, that'll be it. They simply won't do anything about being better even if they could. No matter how much they might protest that they'd love to be better or practise or listen to music. There are heaps more that will never try at all or won't even approach 80% so it's not a negative way of looking at it.
Topic: Fresh meat