This song could be about the French Revolution, it could be about Obama or even Kevin Rudd. Or prehaps Coldplay is referring to the issues in Tibet, however it is clearly about a revolution of some sort and how changes sweep over a civilization and leave old rulers behind inspite of when they have or haven't done.
I think it's definately a song for the current times given the present political climate, as the old leaders die thinking that they have achieved so much for the people, the new Kings, Presidents and Prime Ministers of 2009 and onwards will really be the ones working for the good of all. They will be the missionaries in the foreign fields.