It also comes down to how I decide to end this. Keep in mind that the next book will be either be directly after this book, in the timeline, or very shortly after. It all depends on what I decide works best as an ending. At the moment, I'm deciding between two points.
On a related note, I WILL be starting book 5 directly after this one. However, I'm also going to work on the Five Man Midget Death Squad book as well. Yes, that will be the name of it. I've already started work on it. Normally, I don't like working on two things at once, because I feel like nothing is getting done. In this case, the majority of my efforts will go towards book 5 and the rest to the Death Squad. If I keep up the pace I've been going I should be able to complete Death Squad before Planet Comicon as well as Book 5. If I don't keep the pace, I'll def finish book 5 first. As much as I'd like to have another book to sell at the convention, I'd rather put the fans first. I don't like long gaps between books, especially when it's because the author decided to go off and work on something else. Yes, it's related, but it's not important to the main series. It will be a standalone.
That being said, writing the Death Squad book (thus far) is giving me a chance to really get to know these characters and the dynamics of the team. As oddly important to the next few books as the Death Squad will be, it'll ultimately make for a better read if I develop them completely. From that, I'm glad I decided to start working on it. I won't get into details on that story, I'll probably put up a blog post on that tomorrow under a Death Squad update.