If Bitcoin will be legalized then The price will increase rapidly because alot of users will use bitcoin as currency or can be commodities, the thing here is we have fast transaction and it can be done by both parties. Governments will not going to control us but they will use it for paying taxes.
No I think it would be more stable like gold and any Fiat does. If the government will rule out Cryptocurrency as legal, for sure we will see a major increase of price but it will be stagnant and will slowly be moving.