Nope that cant happen. Maybe after 20 years or something. Many people doesnt even know what Bitcoin is and that is difficult to replace it.
First you must learn them how Bitcoin works and than you can replace it. So maybe later in the future.
You have rightly said! I think this is not an easy thing to happen. It will take a lot of time and also a lot of efforts in order to make people aware of this thing that what Bitcoin actually is. Dollar is a very stable and widely used currency. This will be very much difficult for Bitcoin to compete with it.