uᴉoɔʇᴉq will more then likely won't destroy fiat , Banks and goverments will simply won't let us do that . They will even make their own crypto currencies but It won't be decentralized like uᴉoɔʇᴉq because they like to control .
Now if we speak about the price , yes It's going to rise a lot and if we speak about the users then yes It will rise a lot too but "Almost everyone" ? probably not .
I also think like that a time will come that every country will have her own crypto currency as their national crypto currency, just like the fiat system. But I wish it do not happen, and everyone accept uᴉoɔʇᴉq.
Well that might happen in the future were all country will be using crypto currency and when that happens bitcoin will gone.