Similarly one big change in its legality over the globe can too affect Bitcoin in same way.
The changes in legality is happening right now. By that time (after 10 years) I think Bitcoin standards are already set so there will be no problem in terms of acquiring and trading Bitcoin except if we do not have fund of course/
Actually I don't think creating a legality on bitcoin would be that easy of an affair. Once a country adopts certain legality later they will find some flaws in that legality when people will loopholes and the same would be altered a lot of times before they would be a final verdict on it's legality. Thinking about it this way I think 10 years is a very less time to finalize such laws all around the world. I don't really think bitcoins could become a finalized legal tender in just 10 years.