Assuming you work twenty hours a week, which is an assumption he should explicitly state, rather than stealing it (uncited) from Malcolm Gladwell.
EDIT: edited the OP, added explicit reference to Gladwell. Thanks for pointing that out.
Anyway, putting a number on expertise is purely an academic exercise. The important thing is that it clearly will take a huge effort and "talent" is only a small part of it. The rest is inspiration and transpiration.
I agree with persistence but it seems to me that versatility, self awareness and team Chemistry would be more beneficial that attempting to "become an expert"
The exceptions are, of course, those areas where there are aren't strong diminishing returns (rare...maybe memorization?) or where there is a ceiling on skill (e.g. tic-tac-toe). In those cases, expertise comes with more and less time, respectively.