The question is, what happens to those who already have and
use the kindle/nook ap on their iPads?

can only handle 3,000 items... so that's why apple's
iBook store sucks.

Just use the open source downloads and then upload it from your Linux or Windows box.

Meanwhile, Apple's still got a 2:1 projected margin in 2020, that's how badly they're beating the Kindle.

Even if the woman by the pool in their ad is sexy.

@2 Anyone who thinks they can tell you what the market will look like in 2020 is incredibly misguided.

"What else can they do?"...

Build excellent Android apps and aggressively market them.

Google would soil its servers to have Android dominate in the content market. It would be especially wise to court netflix which is going to be the main provider of instant content delivery in the next 5-8 years (maybe not as measured by bandwidth, but almost certainly by market status).