I think it will be a legal currency worldwide.
It will attract people to try use bitcoin, some merchant will adopt bitcoin, it will be mass. and I think the price movement have more more stable.
The first thing that will happen if bitcoin become a legal currency is it will be used by many, there will be a mass adoption, depending on how it was being described by media and those that has it, a positive publicity will make it prosper, I hope that it is the first thing that happen, but if those news is being toppled by a negative one, bitcoin will not die, but for sure, it will be stagnant.