I see 10% people worldwide using Bitcoin after 20 years. Just like Silver which was $80/ounce in 1980.
I'm sure that in 20 years there will either be very large transaction volume or no volume -- Satoshi Nakamoto
Bitcoin at $600 will also be valuable and will have long term future. Silver at $17/ounce is a precious metal.
I thought you didn't like Bitcoin? 20 years since Bitcoins inception would be 2029. The world population would be around 8.5 Billion by then. If Bitcoin is used by 10% of that population that puts the userbase at 850 million. This is significantly larger than the userbase is today. This means Bitcoin has a bullish future. More users on the network = higher coin price (metcalfes law).
As I have said if bitcoin survives till 2020 in every country across the globe it can then definitely have some nice future prospects, well I am not totally sure if it will survive or not but it should actually even if prices might fall to ground or sky rocket up but if bitcoin survives one day it will be compared to digital gold as it was compared once before.