Not that empires never die, they 'morph' into new forms, but that empires, by their very nature, must die.
Empires define reality; not merely the economic, political, religious, and social structure, but in the very definitions and concepts they use to define and re-inforce their goals.
To change reality, change the concept. [c.b.]
To bring down an empire, all that is necessary is to challenge its definitions. The definitions will always be challenged, again by their nature, because definitions are static and life is mutable.
This, of course, leaves out the minor details of police action, internal bloodshed, death in the streets, and nationalization of resources. Petty details.
Rome fell because empires fall.