Don't expect that price before 5 years, as it will never reach there in a year or two, its too high to expect that price from bitcoin, and the fact is we never know whether it can really reach there or not.
Absolutely you are right, now we can't see bitcoin would be achieved that price $4000 within 2 or 3 years, its take sometime, but it sure bitcoin might be come. But i am surprised why people think too high, if the reality is total different, we should see only present and than make predict.
The price of a monetary asset such as bitcoin only depends on what people think will be its future price. That determines demand and offer at a given price level.