EmtnRllrCstr is right, statistically speaking the chances of their relationship actually working out is extremely low. In fact, this situation could eventually teach your husband a very important lesson in appreciating you and how having a "trophy girlfriend" isn't all it's cracked up to be. It may be she's much more high maintanence, flirts a lot with other guys, there's all sorts of possible negatives and now he'll get a chance to deal with those.
And actually them moving in together is probably the best thing to "test" their ability to live together, get along, deal with the reality of the situation, etc... It's no longer two people only showing their best sides to each other. When you live together the ugly stuff comes out. Maybe she's grouchy or gassy in the morning, maybe he leaves the toilet seat up in the middle of the night.... I'm sure he wasn't perfect to live with, but you both had history together, kids and had probably gone though a lot of good and bad over the years. You had time to build a relationship. And you put up with his bad qualities and moodiness (I'm sure he had his moments. Don't tell me he was perfect!).
Anyhow, don't worry if he's coming back or not. Would you really want him back at this time? I know you think you do, I remember wanting my husband back so badly, but I also began to realize that I wanted him to want me back. I wanted him to learn that what he had was pretty good and the only way for him to do that was to experience something else. Not a pleasant thought, but important at that time. I didn't want him thinking "what if" about OW and wondering if she might have been the better choice. I wanted him to get her, and the idea of there being something "better" out of his system. Otherwise, I figured it would just happen again.
You really have to stop worrying about your husband (I know it's easier said than done!). Read, self-help books, maybe get involved in your community (what better way to make friends and get to know people!). By the way, if you do find yourself feeling very anxious, depressed, sad and obsessing about all of this, you might want to consider going to the doctor and inquiring about low dose antidepressants. This is something I never would have considered for myself, but at one point I decided to look into it and went on something like 5 or 10mg of celexa. I'm generally very antidrug, but this ended up being a good decision. It did seem to help me focus more on myself and be more positive about things. Even just a little bit took some edge off during a very difficult time in my life.
There is no arriving, ever. It is all a continual becoming.