I don't know about Amazon. But as soon as A4 color e-ink displays become available, Apple is gonna enter the market with a dual (LCD-eink) display product. Probably a tablet.
As for content they are gonna go for magazines rather than books, since people tend to consume more mags. Mags are bigger market: easy and colorful. That's Apple.
They could sell a matching bluetooth keyboard accessory for productivity apps and just forget about the macbook air.

They'll obviously call it the MagBook.
and the year it launches Time will run a cover story on it.
The tittle: "The book of Jobs"
(But UIs are so important for Jobs that he probably won't use e-ink until he can display video...)
What do we know about Kindle 2.0.... just that it's gonna launch internationally. (hope so)