This is a fallacy.

It's rational to buy stuff when it's cheap and sell stuff when it's expensive. Not the other way around. In other words, if the money gets suddenly more valuable, people would go on a shopping spree, which would cause inflation and the value would return back to normal. They wouldn't wait for it to be even more valuable. The situation would be different if there was a guarantee of deflation, but there isn't.

Economic demand is driven by human needs and wants. Lot of everyday consumption, like food, is bought when it's needed, and can't be bought 5 years later, because you'd be dead already. Other things, like a computer or a car you can buy later, but then you'll have to make a calculation whether the thing is more valuable today or after 5 years if you'll get it 30% cheaper. There's no situation where you sit on a pile of bitcoins and just die there waiting.

You're trying to rewrite decades of economic theory in a single comment. You can just Google "deflation great depression" and "elasticity of demand". Think about the opposite side of the coin. You have car that is ok but want a better one. The better one costs $35k. In a few months, it will be $30k and a few more $25k. When will you buy it? Deflation is kryptonite to consumer spending.