Many economists argue that a deflationary economy is a disaster that should be avoided at all costs. That is because in a period of rapid deflation, people tend to hoard money instead of spending it, hoping that prices will fall. Such a phenomenon unfolded during Japan's "Lost Decade," when a complete collapse of demand pushed the currency into a deflationary spiral.
This is irrelevant to Bitcoin because Bitcoin is not a widely used currency, so whether people HODL it or dump it, there will be no macroeconomic effects.
If we imagine that bitcoiners just decided to never sell their coins, the price would skyrocket, and so will the temptation to sell at a huge profit. But it's just an unrealistic scenario, so I don't see any point thinking about it.