Would a larger toy like this show up one eBay? I don't recall items like the Y-Wing and ARC-170 ('07) showing up before public release. I guess the various overseas markets might receive the Rancors before the US, and that's what I should lookout for.
After thinking about it, I could see how an eBay store (Black Sheep toys, is it?) might start stocking the rider figure, and that might be a sign of a close release.