The most recent fuel that's fired the Apple-Tablet Rumor was large orders put in for particular screen sizes. It seems really unlikely to me that Apple would release an eInk device, let alone one which has a technology which is still in the early prototype phase.
Apple's recent tech moves have been largely about releasing tech "done right", that is to say, improving upon existing technologies. I'm still pretty skeptical about the tablet rumor, but less so than I was 3 months ago. I don't see Apple pushing this as an eReader...