Never. My conclusion is that while Bitcoin is useful, it's not THAT useful. It won't be eternally cheaper than other payment solutions, and it has its hassles. While it has way to go, I think it's grossly overpriced at the moment; the "natural" value of Bitcoin should not be over $20. So, in order to be "naturally" valued $10,000 the adoption should grow five-thousand-fold. I think this is unlikely. Not impossible but very unlikely.
If this does indeed happen, I'm going to be filthy rich.
Where did you come up with the "natural" value of Bitcoin as $20?