Will bitcoin ever replace currenries we have today ?
It might happen, but a sort of a revolution has to occur whereby people will lose faith in centralized monetary system i.e if they don't think their money is no longer safe.
maybe an
1/
8th of the worlds population
It wasn't 1/8 of the world's population but we saw it happen during the Cyprus banking crisis. Suddenly Europeans went on a BTC buying spree presumably because it was seen as a hedge against "bail-in" bank account seizures.