Still, I agree with the premise that after next halving it is not unrealistic to expect that value of Bitcoin will reach a price of $50 000. Amount of money needed for that is in fact very small if viewed globally, only about $800 billion - for example US budget for 2020 should be around $4.7 trillion.
It's not unrealistic if we look back at what happened in the past, but we shouldn't discard the possibility of not getting there. People always assume that there is so much latent demand, but that's only based on the historical trend.
My long term target is $100k for Bitcoin, but I'm perfectly fine conceding a counter argument as to why we won't be getting there. Bitcoin might be small in the grand scheme of things, but that still doesn't mean it has to or will grow further.
I at first was wondering why some Bitcoiners were cashing out around the $20k mark, but that's more than understandable where they come from. You have a $20k price to sell at, so you take it before you never see it again.
I expect more old hands to unload the closer we come the all time high. Realistically speaking, what's there to lose out on? It's not the same as how things were when people were selling around the $100 mark to heavily regret it years later.