I don't think that makes much sense. It is possible that Bitcoin reaches this value someday, but it will not make people stop using fiat. To gain more users, Bitcoin must first reach more people willing to sell goods and services for Bitcoins. In this way, there will be greater liquidity in the market, and over time Bitcoin will gain more stability. This will give more confidence for people to use Bitcoin as a currency.
Exactly, some people will keep using fiat till the end of the world. Right now bitcoin is in beta stage and still exploring itself and I believe that we are in early stage because bitcoin is going to lasts long. Bitcoin will gain space in day to day transactions, both local as well as international but still it wont ruin fiat (of any country). In most successful case bitcoin might reach the level of fiat but it wont destroy fiat because its the way we are using so far.