Bitcoin will always have the highest volume. Litecoin has been second (worldwide) for a long time. Monero and Ethereum both have a good chance to challenge Litecoin for both wordwide trading volume and valuation within the next few years.
Perhaps one day the newly independent Colonies may act as a "little brother" supporting nation for the British Empire (or whatever European country is dominant at that time). European currency has been the dominant capital of the world for centuries and it's silly to think that will change any time soon.