Bitcoin will come likely do not destroy the banks it may become mainstream but not that kind of mainstream.
It might go mainstream. I believe by 2020 most of the people would be aware of bitcoin but most of them won't be using it. I think bitcoin will be almost every people of china.
I think china will be first country to have accepted bitcoin as a real money in the future and will be used by most chinese people living there since they do have a the large amount of miners for bitcoin.
bitcoin has potential to be that big. Think about diamond. It's a valuable item, just like bitcoin, and there is a hard cap of it, just like bitcoin.