In what file-format will books be distributed now (in the future)?

There are many formats at which ebooks are currently distributed. The three most common formats are pdf (portable document format) for windows, mac and mobile devices and chm (Microsoft Compressed HTML Help) and lit (microsoft reader) just for windows. Amazon uses its own azw format for its kindle.
http://en.wikipedia.org/wiki/Comparison_of_e-book_formats