Todd, I'm sure you're right. When the movie was first offered for pre-order on Amazon, it was listed as being available as a standard 3D edition, and cover art was posted -- it wasn't one of those placeholder preorders where you don't actually get any product information. Then it was outright...
It's funny how they seem to love that there's a 3D version when it comes to the theatrical release, but then get skittish about it for the home release.
Studios have in the past made the claim (rightly so, I believe) that 3D can be so much more than a gimmick, and can really enhance the film...