Hasbro said that there have been plans for a Dietrich figure, but they canceled it before one could be made. Why wouldn't they just bring it back if they're doing the same for Satipo, Toht, etc.?
Those figures actually made it into pre-production. Molds were made, prototypes created, etc. As far as we know, Dietrich never made it off the drawing board (if he got that far).