When Barnes & Noble Chairman Leonard Riggio sold nearly a quarter of his stock this week, some saw that as a sign the game was over. Here is the stock market's reaction, covered in The Wall Street Journal (sub. req.)
What convinced me that bookstores are irrelevant is that clients don't care about their books being in them. Their concern is with Amazon.com. And it's the whole continuum from having it listed there to boosting rankings. They can't even imagine anyone actually going to a bookstore to buy a book.
If bookstores make it to 2020, they will be reconfigured into some other entity.