~ and we know that the moment btc becomes very scarce, people would no longer panic sell, they will hoard their coins and then continue to quote very high rate for it which will gradually make it become so expensive, and as it becomes expensive, we will start migrating from bitcoin to satoshi, then maybe 1 usd would be equal to 1 satoshi, this is why those that predicted bitcoin at $1m must have seen.
If 1 USD equals to 1 satoshi, it's $100 million for 1 BTC, not $1m. But this will never happen imo. Once I calculated what the price of 1 Bitcoin would be if it replaced all the money in the world, and I came to around $4 million for 1 BTC, although this scenario will hardly unfold either. What can happen when Bitcoin becomes very scarce(or even any time today) is that it can become a trend among millionaires to have 1 Bitcoin in their possession. This one thing along can increase BTC price to the level of what amount of money can a millionaire spend on collectibles, but I think it's much less than $1m, although it can be around $100k. (Note that there are 36 million millionaires in the world already, and there will be only 21 million Bitcoins ever.)
