iPhoneGeneration.iPad2Gen (and maybe iPhoneGeneration.latest)! Cool, if you could add this! THX
latest makes no sense as that is no hardware nor even stable over time 
The enum will be changed soon - check out this thread for more information.
Quoting seliongames: iPhoneGeneration.Unknown shows up in the editor, but it does not appear to be in the docs on the iPhoneGeneration enumeration page.