Because I'm waiting on it, too. In fact, I'm the one who introduced Rina to the series. For that matter, if I was asked for the two authors who'd influenced my writing most, I'd have to name Tolkien and Paolini: Tolkien because he did everything so well it drew me in, and Paolini because he started doing things so poorly I knew I could do it at least as well. (Tolkien's first drafts helped, too.) Still, his plots are interesting, and he's definitely worth reading at least once.
The first book... well, Paolini already knew back then how to do gripping beginnings. Next, unfortunately, we see Brom tell the top-secret tale of the Empire's beginnings to the whole town; then, he and Eragon run off to learn magic and... do nothing in particular. Then Eragon dives into danger to rescue an Elf who... is beautiful. Yes, I know the Empire is evil (though you've only got Brom's word for it at the moment - and, yes, they killed your uncle for letting you keep a WMD around), but for all you know, they locked her up for a perfectly good reason! Like, oh, putting love charms on innocent farm boys! Well, Our Designated Hero somehow gets out of that situation, and he's on into the next book.
Despite this, I kept reading, and Paolini improved. The Battle of the Burning Plains might've been unrealistic, but it was much better than the Battle of Farthur Dur. The trilogy might've expanded into a tetrology, but it stemmed from a good decision: he'd defined Eragon's character well enough that he knew Eragon couldn't just fly off with Saphira but would have to stay behind and deal with Sloan. Roran might've not been the best choice to lead the village in Book II, but it's better than letting Eragon and Saphira fly through an ill-drawn world. I'm confident Paolini will improve still more as he concludes it in Book IV.