I think reusing the Opteron name is really not a good idea, since now there'll be x86 Opterons and ARM Opterons. Maybe Apteron would've been a better choice...
I think AMD are positioning this for the server market (though would love a nice cheap desktop with this chip. With that they are levridging there only real asset in branding and I feel it will not water down but help the Opteron range live on, given they are moving away from the x86 area.
I agree that re-using the name is bad mojo from a marketing perspective, too many people will be caught off guard by the lack of compatibility with the x86 chip set.