Bitcoin is engineered to be volatile. A market determined rate of supply would increase or decrease with demand, stabilizing the price. But Bitcoin opted for a centrally planned rate of supply, artificially fixed in advance.

Which means there's no stabilizing mechanism. That's why it can never be seriously used for budgeting, stocking, nor performing accurate economic calculation in advance.

I wouldn't bet on the price not swinging both ways forever, as it was designed to (and the reason people see Bitcoin on the evening news).