When is Christopher paolinis next book coming out?

On randombuzzers.com, a few months ago or so, Christopher Paolini was answering his fans' questions, and one of them was when he will finish his next book. His response was that he was not finished, but was kinda' close, as, when he was writing the third book, he found that it was going to be too long, so he ommitted some so that he could fit it into the fourth book.