Makes sense. Rogue One is Star Wars in most people's minds for right now, right up until episode 8 comes out later this year. I'd be willing to bet that the vast majority of Sideshow's prospective buyers wouldn't even know who IG-88 is.
The only surprising thing to me is that we didn't see a life-size BB-8 announced alongside The Force Awakens. Talk about brand/character identification... that would sell like crazy.
blasphemy! : )