From a marketing perspective I'm not sure a 650 Himalayan would make much sense. While the Interceptor is a terrific bike, it is, at least in the US, very niche oriented, and has very little competition. It beats the Triumph Bonneville on price, and in many examples performance, and I think it puts the W800 Kawasaki on the trailer in every respect.
A 650 twin ADV bike would have to compete with several very good bikes that are well established in that class, and while they are somewhat more expensive, I'm not sure the guys that buy those bikes would be concerned over saving a grand or two.
On the other hand a I think a "scrambler" variant of the Interceptor, think of the first gen 2008 Triumph Scramblers or even a 1970 Honda CL might sell quite well, as would a larger displacement Himalayan.
In any event it'll be interesting to see what they come up with. Perhaps a 350 Meteor with a high pipe, braced bars and skid plate?