Bitcoin already is a world currency from the position that is used by people at almost every continent in the world. But because of the reasons that you have described it will never be mainstream currency or official currency in some country. But from my point of view that wasn't the goal and it shouldn't be the goal of bitcoin.
Also the fact that through internet connection bitcoin is available all over the world makes it global and gives opportunity to all nations in the world to use it and that is the beauty of bitcoin.
Yes, I believe many people aware that many countries now adapt bitcoin in their country as an alternate currency and many businesses in other countries in the world already accepted bitcoin as payment and this is a strong evidence that bitcoin can be a global currency.