Why I said not selling next year might be a wrong advice is because most people have their profit target set and that could be triggered next year, to me there is nothing wrong or bad in taking profits it is even the essential reason for investing in the first place. So the advice should be take your profit when it triggers and hodl if you can for another extra four years
If you are a long term holder, it's very obvious that as long as you haven't hold up to 10 years time, you wouldn't sell regardless of the value of Bitcoin, because with the kind of huge potential of Bitcoin, it can go as high as a million dollar in the future.
But if you are those Bitcoin traders that sell for minimal gains, you will sell all or even some of your holdings when you are already in a profit, so it all depends on who you are, a long term investor or a trader that sells for minimal gains.
So I wouldn't say it's a bad advice because it all depends on the angle you are looking it from, which from my own angle the advice is good, except him advicing that we should buy enthereum which isn't as trustworthy as Bitcoin, apart from that his advice is good.