Now that I've thought about it a little more, and read some of Adam's comments, I have a different theory. That being this exclusive may be the way to release the last few remaining characters from the Kenner line (up through POTF) who have yet to be re-made in modern renditions.
Adam has also mentioned in some comments at a couple of other sites that this set will be unveiled before the weekend, and will not include characters from either ROGUE ONE or REBELS.