If Bitcoin is an experiment, as Satoshi Nakamoto has advocated, then what are the real chances of it--Bitcoin proper (not some other crypto-currency)--truly becoming mainstream?
What is your definition of "truly mainstream" ?If 1% of the world uses Bitcoin for 1% of their transactions, then I'd still consider it a huge success. I think there's a good chance that happens, but that doesn't fit my definition of 'mainstream.'
I think there is small possibility Bitcoin proper is used by a majority of people in some country somewhere in the world use it at least once a week to pay for things. I'd consider that mainstream success.
I think there's a tiny possibility Bitcoin will eventually become as popular as the dollar.
But I'm not very good at predicting the future, so you might want to consult you local fortune teller.