his claim at the end of 2019,
It should not necessarily be at 2019. "When" is not defined at his post.
I understand, but normal people will state the year, or the actual timeframe if it was not the year 2019.
For example, one would say that it will drop to 775 by 2020, etc. If nothing is said, then 2019 would be implied.
If he is using indefinite timeframe, then anybody can make any predictions. I can say all cryptocurrency, gold and stock market will drop to zero, since eventually Sun will enlarge and become red dwarf, engulfing the entire Earth, and everything will pretty much go to zero $USD.
So my point is that by making a statement without ANY timeframe, that statement is essentially meaningless. Since I'm sure that Armstrong was trying to make a point, my best guess is that he implied the year 2019.