Mike is smart, very smart this paragraph nails the problems of booksellers and publishers too:
One distracting fact for analysts considering this question has been the apparent slowdown in the growth of ebook sales, suggesting that there are persistent print readers who just won’t make the switch. The encouraging fact is distracting because it is incomplete as far as predicting the future of shelf space at retail, which is the existential question for the publishers, wholesalers, and bookstores (and, therefore, by extension, for legacy authors too). We need to know about changes in the division of those sales between online and offline to really have a complete picture. If ebook takeup slows down but the online buying shift doesn’t, the bookstores are still going to feel pain.
via The future of bookstores is the key to understanding the future of publishing – The Shatzkin Files.
Eoin Purcell's Blog 
I belong to a group of readers who reply to surveys sent out by Random House. Towards the end of last year there was one about ebooks. When the results came in, 6 out of 10 had bought an ebook in the past year but only 2% had switched over to ebooks completely. I think ebooks will continue to be a part of the market, but like audio books they will need to find their niche amongst the multi media. Happy New Year, btw, Eoin!
And to you! I reckon their Niche will be the largest share of the market for most fiction and narrative non-fiction! I’ve switched pretty much all my books digital!