After months and months of writing, editing, publishing and promoting a book it's very hard to set your mind on a new one. In one hand, you have all these new ideas and characters clinging for your attention and wanting you to sit down and start writing. But on the other hand, you have your newest work struggling to reach the right audience and urging for reviews. And it's extremely time consuming to get your book out there when you're not a well-known author.
Now try to balance that with a full time job and a family and you get a taste of what a new author's life can be like. Still, I wouldn't trade it for anything in the world and I won't stop doing it until I'm able to write full time. So fans, be patient: your favorite author's next book may take a while to come out, but it will eventually.