We can't really tell, maybe there will be a lot of nations that will follow El Salvador path's, specially neighboring countries in Latin and South America. Or maybe some in Africa and Asia as well.

So this is a just a beginning, in my opinion. If developing or underdeveloped nations find that bitcoin or crypto will help them a lot then why not? But don't expect though that bitcoin will become the world's financial instrument, I doubt that it will happen, the US dollar is still the king.