It's probably something that would not happen in a few years, but I believe there will come a point where the number of users, who will realize the benefits of using Bitcoin, will increase at a rate never seen before.
I think though users bitcoin is growing and very much it would not make bitcoin replace fiat, it's a sure thing! but for a price of course there will not be people who know about it, maybe the price will explode
It will not replace fiat currency because bitcoin is compatible as well and it can be converted with each other specially of online wallet transaction without fiat you cannot hold cash in hand when you cash out your crypto currency to fiat currency. Thats why bitcoin cannot replace fiat as well and most common reason fiat is very important to bitcoin they are somewhat partners of online transactions.