It's absolutely fair to raise the question. What I'm suggesting is that it's an open question. I think the deflationary argument against bitcoin is compelling. And, yes, it's absolutely possible that spending could drop drastically as the value goes up. But, here's a question: Has bitcoin spending dropped drastically as the value has gone up? What's so important about the future values of $500, $1000, and $10,000? It seems there's enough history now that we can scrape together enough data to make some preliminary judgments.
What's important about future values is people's reaction to increased ROI on their investment. The pizza scenario is a perfect example. If you can buy a pizza today for say 0.1 BTC but in a matter of days (or whatever) that same 0.1 BTC could be worth $200. Arbitrary numbers but I'm just making the point that people's willingness to spend something that continues to prove that it not only will be more valuable tomorrow but is actually designed to be that way, very well could stagnant spending. As ones confidence grows that Bitcoin will be significantly more value next month than today, spending them makes less and less sense, from a investment stand point. Which is obviously the point the article was making.
I understand all of that. The point I'm making is that that article could have been published 4 years ago, and, in fact, people did write such things 4 years ago, and 3 years ago, and 2 years ago, and last year. And, yet, it seems, at least anecdotally, that spending has not stagnated. What I'm suggesting is that we don't need to speculate about future values. We already have a history of deflation and possible increased spending to explain, which runs contrary to the deflationary argument.