Its possible but it make take decades before it happen. Bitcoin may increase its value but it will have a hard time to get in the main market around the world. Maybe the whole cryptocurrency can be a good alternaternative for a fiat money but it will never be the main currency I think. Our government will always find ways to protect fiat money, but a least cryptocurrency will be accepted around the world in the future.
I agree with you because of its volatile price crypto currency will remain an alternative for fiat money, but who knows if the society accepts it and make it as permanent currency, it will be good actually, and Im sure that crypto currency is still developing its features that can be use in mere future, lets just wait for it to happen.