not all will become millionaires since there are people who will sell their coins at a lower price due to financial reasons and I think not all people who invested in it have enough amount of coins to be millionaires since not all have the same amount of coins invested.

that will be impossible since fiat is here far longer than the governments we have today so the system of local currency will not be replaced because its easy to spend cash than digital currency.

well as of now the transactions are very high so you should expect that amount for fees. but after a few days the transaction fees will be lower so if you can wait for that if you are going to have another transaction the better.

of course not. The price of bitcoin mostly as of now depends on the law of supply and demand and we can all say that bitcoin is the most used cryptocurrency as of today and that alone is enough to make it stable for a very long time.

well many will withdraw their investments and the value of bitcoin will surely drop if that happen.