What code edition are you using in AZ? The change to 4 wire was first required in the 1996 NEC, so this isn't exactly new.
To answer your question, from the 1996 NEC on requires 4 wire circuits in all new installations. Old 3 wire circuits are permitted to remain.
A feed to a dryer or range that is 2-wire with a bare ground has always been a code violation, and should be replaced no matter what.
Peter
[This message has been edited by CTwireman (edited 08-31-2004).]
