Other devices made it big using a subscription model. Sell the razor cheap and charge for the blades. What if a company, say Amazon, came out with a continuous subscription model? Say they charge $10 a month and you can have one book loaded at a time (or $12 for 2 at once or...). The price point is arbitrary. I have no idea what the market would bear. They can download a new book and delete the old book at will. Sounds like this Netflix model is something the Kindle might be capable of doing.
A lot of us might balk at never actually owning the books but isn't this a path to financial success? They can lower the reader's price because it is made up by a guaranteed income stream.
My other thought about the market is a bundled sale. I'm not sure how it would go over. What if you offered the reader at a reduced price because you are buying e-book store credit at the same time? For example, $450 for the Sony reader with a $300 store credit. This would hit two birds at once, reader price and guaranteed publisher income. Might not fly well because of the higher initial investment. That's why I like the subscription concept better on its chances for success.
If we could access enough books at will would it matter that we never owned them? I think that could induce the paradigm shift to ubiquitous cheap e-readers.