Neither is exclusive in any form.
Spector is a 30th anniversary figure (thus not pushing other figures back) and a brandnew character, to cope with the theme of the 30th anniversary figure line. Illumina is an existing character and therefore may be already slotted in for a regular figure somewhere down the road. This is as far as I understood Scott. She is not only in the cards, she is slotted in the roadmap, somewhere far down the road, but she is in.
Pushing for her, to release her sooner than later would mean pushing back on other figures. Same as if the fanbase would suddenly start asking for... let´s say Gwildor, who might be slotted in for 2013. This same "vocal minority" starts accusing Mattel for not wanting to make Gwildor, even though everybody SHOULD know, that Gwildor, being an "in the cards" character, will come sonner or later. Nevertheless, everybody is asking, then demanding, then trying to force Mattel to release Gwildor sooner than later. Mattel would answer with the very same statements. Releasing Gwildor "now" would mean pushing back all the other figures that are already slotted in. This might include Lodar, Spikor, Evilseed, Darius and Frosta. Woop-dee-doo! Here we have Gwildor, as fans demanded. Lets just wait even longer for other fan-demanded figures then.
So. Let´s PLEASE just wait and see. Illumina will come, I am sure. And as much as I like and want her, I´d say let´s stick to the roadmap Scott created and be patient.