Will other inspector guns be coming out? Good question! I was wondering about that myself and about the only thing I can suggest is giving USFA a call and asking. Looking at their web site, it would appear that, in addition to the Nettleton series, there will be Ainsworth, Clark and Carr series guns as well.
I doubt if that will take "pre-orders." I have noted, in the past, that USFA does not take orders until guns are actually in production.