Was Fraction planning on continuing past #16 (or whatever issue it is that finishes up his big stories) in FF & Fantastic Four before he made the decision to step off, or had he planned on writing those issues and then leaving at the end of the big stories?
Matt’s ongoing storylines were all intended to wrap up at #16 of each book. At that point things could have gone either way–but I would have tried to convince him to stay on longer.