The book won't go ahead, basically. I can't afford to front the cash myself, and I would never ask, expect or accept any work-for-exposure deals for contributors.
Although the book itself won't exist, and even though no money will be changing hands, I intend to provide some rewards to people who pledged support to the campaign.
Should I attempt to put together a book like this again, I would probably end up doing most of the creative work myself, using my own ideas.
As for the people who have already made story submissions, they will (obviously) retain all rights to the pitches they have made. In the event that at some later date, I want to use one or more of the ideas pitched to me, I will be contacting the creator directly, and will attempt to buy the rights to use their idea for a fair amount of money (and they will still receive a writing credit).