I'd say that if your app is not ready and you aren't taking the DAT for another month, it is probably too late. But if you have outstanding stats, you may still have a shot. Just realize that some schools (not most) already have interviews booked through November.
If your stats are good enough, then you're fine. Also depending on the school you're applying too you'll have a better chance. For example, Case may have filled their interview slots but plenty of other schools haven't even started offering interviews. That being said- you want to submit it as soon as possible