Well, Im on iOS 7 now, and there is definitely NOT a quick reply. On the other hand pretty much every app you use stays running in the background so there is like no transition time save animations
So that you can reply to an iMessage directly from the notification itself without jumping into the app.
The more I see how notifications look right now, I think it is something that they may be looking to implement in a coming beta. The reason I think this is that the notification banners are very large vertically. It doesn't make sense for them to be so big without any additional functionality other than showing that you have a notification with a preview.