I think it's great that he has been so well recieved. Perhaps the commonwealth may hang on after all.
The Commonwealth is in danger from total disinterest amongst the people of the member nations and has nothing to do with the desire among many Australians for us to become a republic.
There are many republics within the Empire with India being the largest in terms of population.
If and when Australia becomes a republic the other member nations will get to have a vote on keeping us but other than that there will be no change to the status of the Commonwealth.
The Commonwealth has over 50 nations. Most of them are republics now.
However, for most people the Commonwealth has very little meaning - sure the Commonwealth Games happen every four years - this year in Delhi but there is a possibility of some countries not attending due to fears of terrorism, with England (and I assume the other countries that constitute the UK - at the Commonwealth Games Scotland, Wales, Northern Ireland and each of the Channel Islands all compete separately) - having talked about not going and the Australian government has said that it will assess the situation closer to the time.
Other than the Games we don't hear about the Commonwealth much. Even when the Heads of Government meet and the Queen attends, unless the meeting is in Australia itself we usually don't hear much about it. I head more about CHOGM on this board than I do anywhere else, usually with people commenting on what the Queen is wearing and not about what matters were discussed.
For the smaller and poorer nations it might have meaning but for many Australians it means very little, if they are aware of it at all.
In our NSW History course where we teach about Australia in International Organisations the Commonwealth doesn't get a mention but SEATO, ANZUS and the UN do. That is the mandatory course that all students must study.