While not a huge surprise, the original 1960s series creator (and patron saint of toy fans) Mel Birnkrant has confirmed he is currently designing more new aliens for future series of the action figure line. Via the Fantastic Exclusive forums:
"Believe it or not, today, I’m working on sketches for OSM line extensions. Just getting started really, but I think I have some exciting ones in mind."
While not specific, it does confirm that the line will probably go beyond the initial 7 released figures and 6 proposed and unreleased ones. For his original 1960s sketches (of which that illustration is one), visit Mr. Mirnkrant's galleries on his web site.