I'm not going to start on the fourth draft just yet. I plan on reading the novel as it currently is, take some notes, and then step away from it for a while. I usually need a break when I work on stuff like this, because sometimes I'll get tired of a piece of work if I spend too much time on it. That way I can come to it "fresh" after a break of at least a month or so.
The next book in the trilogy will be called Wilders. I've been outlining the other two books, and there are still a few additional details I need to work into The Distant. But with the outlines nearly solid now, I plan to start on the first draft of Wilders any day now. It will be good to write for a while instead of editing.
I've been playing with potential covers for the books... still haven't decided whether I'm going to ask someone else to create the art, or do it myself. The only thing I don't like about actual cover art (i.e. a scene from the book) is that it may mess with how you imagine the content with the book itself. Especially if the art is bad (like The Wheel of Time).
So if I do them myself, I'll do it without an actual scene, but instead will do something simple, but catchy... probably involving symbols of some kind. There are some in the books that would be good for the covers. I have an idea of what I want for my versions, and did some mockups a while ago. Time will tell whether I use them or not. But it's fun to play around with them and see what I can do.