Convergence

Network resources will always be heterogeneous. They will be based on a mix of different technologies with different functionalities and programming models.  Note to technology bigots:  every technology has a finite life and will eventually be superseded.  X.25, SNA, ISDN, ATM, Banyan vines, Novel Netware, all had their day.  I am sure that you can think of a few more technologies to add to the list.  Technology evolves.  New methods become available that obsolete older methods.  

Ethernet has matured from an interface, to a service, to a transport-network. Cost and revenue considerations will inevitably drive network expansion that is biased toward Ethernet in all three of these dimensions.