Sadly, there is no guarantee that such a thing can't happen. In some countries, bitcoin doesn't pose a threath. Also ,it doesn't harm the economy. At least, not yet.
But, for other countries that are facing problems, it is indeed a threat. Some transactions need to be tracked, for people 's safety purposes. For example, imagine that an assasination happened. The government caught the hitman and the money he got from the opetation. They want to track it. If it is in bitcoin, they can't. In that case , they will just prohibit it.
What i want to say , nothing is certain, because its happening , depends on too many variables.
For sure, this matter of bitcoin legalization and illegalization throughout the world is not a small thing. It is moreover dependent on various factors such as the government system of the state, economy, crime rate, demographic variations etc. so it is not easy for the state to take nay solid step in short time. Here I will appreciate those countries that have declared bitcoin legal because they are step ahead from others in understanding the need of this action.