13 years is a lot of time. Almost double as much BTC exist. Price can be any high. You also need to understand that you will be able to buy way less with $500k as you can now. Somewhere from half less to way more less. So when you measure BTC value for so long you should use something else then $. Maybe Gold or Bread.   But in general such long predictions are useless. Rather predict price at year 2020 or if you are brave at year 2025.