Isn't it alreday an international currency? I think it is. Since people around the world begun to use it it has begun global, international currency. Today I think it is used on all continents. Will it be officialy recognized as such, that is another question.
You are right it is already an international currency as we are seeing that none of the country is its owner and all over the world this currency can be used and people use this currency for their international transactions etc.
I do believe op is asking when it will be recognized by the others currencies, and not asking about when bitcoin will become international. Its already international as we send and receive payments from others and the most arent from the same country.
If he's asking about when it will be recognized, I hope he realizes that it is a long ways away until Bitcoin is recognized as an international currency, if it is ever recognized at all. It just comes down to whether or not Bitcoin can be common enough that people buy it and start to use it consistently within their own countries beyond the reaches of the government, and whether or not it could get a high enough market cap for most financial institutions to become a thing.