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.
Whatever would be the value of bitcoin, yes it won't replace fiat. This is already a long discussion whatever would be our speculation, no doubt that bitcoin won't replace fiat no matter what happens.
Government will not risk the financial system into a decentralized crypto currency and has a limited supply that can't be supplied if they want to.
You seem to be missing a few important details in the "bigger picture"
I'm also inclined to think that governments in general are not going to endorse Bitcoin use in any possible way (apart from accepting it as a foreign currency of sorts), though the Swiss government may disagree with this. But that's not my point. Important details that I'm talking about consist in the possibility of governments themselves going away at some point in the future given the overwhelming tendency of the world becoming a tighter place overall, primarily through Internet. In this way, whether they like Bitcoin or dislike it may turn to be irrelevant in the end
It might be possible that governments will see the potential of bitcoin but they won't accept it as primary currency but as an secondary currency. But whatever will be the bigger picture you are pointing. Governments will not going to allow bitcoin to completely replace the their local currency because they have control for it.