This number will decrease a lot over the next 20 years, and I believe that at some point we will achieve a 30% increase in just 4 years, and after about 40 years the price may be stable and the rate of price change in Bitcoin is 10% over 4 years.
Therefore, the idea that you buy 1 Bitcoin and think that it will reach several million dollars or will increase, even by a percentage close to previous increases, is illogical.