Guys, I don't like to be a buzzkill, but I wouldn't get hopes up. These petitions almost never work. You would need thousands of signatures, within basically a week or two, to even get LucasFilm's attention. Furthermore, they've clearly made their decision, and it's based on realities of the publishing industry: to push the book up to a June release would lose more money than it would take in. They wouldn't have time to drum up publicity and all that sort of jazz. By contrast, if they didn't publish it until December or so, all the corporate marketing synergy would be gone, due to the different release times.
Maybe they'll release the eBook, but I'd be shocked. George Lucas hasn't cared what his fans wanted since...well, since ever, really.