I'd honestly be surprised if you saw rMBP's launched without OS X Mavericks. Really think Apple is going to package those two together as Mavericks is basically the software rewrite necessary to properly eliminate any remaining lag. If they launch the hardware on Mountain Lion there's going to be too many reviews nitpicking any lag they find and turning it into a major flaw.
Suspect the September event will be iPhone, iPod and iOS 7 with the possibility (if the rumors are right about a split launch which, let's face it, isn't exactly guaranteed) of the iPad refresh as well. Then an October event doing rMBP, Mac Pro, Mavericks and the new Mini (especially if it does turn out to be a non-retina version and a relatively minor upgrade).
As for the iPhone 5S there's a bit of me that wonders if Apple are going to go in a slightly different direction and focus on battery life. After all they're basically following their own path on SoC design now and as someone else said the iPhone 5 isn't exactly a slow device. Considering the relatively low resolution compared to the monster full HD panels that are in some of the big Android handsets I wonder what the impact would be of going to a single core Power VR 6 GPU in the 5s... Probably not of course, but it's a fun thing to ponder.