What I'd like to make you look at is USD to BTC chart (rather than usual BTC to USD chart).
https://imgur.com/UD0pSDII approximately marked the drop with the blue lines, and you can see that the drop of value of USD compared to BTC is quite linear in last couple of years, and it gets closer and closer to 0. Even the monthly graph is the same.
Sure, if you look at the graph from the invention of bitcoin, you could see 1/e
x graph instead of linear one, suggesting that the drop towards 0 would be quite slower than with linear drop, but the yearly graph is actually closer to being linear.
So while we usually easily see that BTC grows compared to USD, I think that sometimes we really forget what that means other way around, how fast is USD actually plummeting down compared to BTC.
I'm not trying to be too accurate here (as you can see from the graph, I didn't bother to put the exact calculated lines there), because it actually doesn't really matter. Instead, the moral of the story is, even the bravest predictions don't look too impossible at this point.