Are we moomin, or are we dancer?
Doesn't the diminished time and greater responsibilities that we come to possess when we grow older factor in most people's capability of working on their potential talents? Provided such talent is not intertwined with one's career, or such.
I had a remarkably easy time learning foreign languages when I was a kid, but now I do find that it has become increasingly difficult to really learn new things as I did back then.
I don't feel brain "plasticity" plays as much of a big role in limiting potential as one's circumstances do. If only everyone had the resources to completely dedicate themselves to working on what they have an affinity for...
Studies have isolated brain plasticity as the leading variable. It is still possible to learn foreign languages, and become fluent, as an adult. Children, however, uniformly outperform adults, intuitively picking up subtle pronunciations and intonations that their elders struggle to imitate.