M16/AR15 is clearly an Icon already.
The better question is: When the U.S. Military moves to it's next main battle rifle, what will become of all the M16A1's, A2's, M4's, etc? Will they be "converted" to semi-auto and re-sold through the CMP? I know LEO's and their depts. can already purchase M16A1's through a certain program (name escapes me now).
If the actual military weapons can, at some point, be used by or sold to civilians, the M16/AR15 platform will cast a long shadow over Grandfather Garand.