2 iPhones, 3 iPads and a new Apple TV does seem like a lot to get through in one event, especially with iOS 9 and Watch OS 2 as well. I'd have though the iPad Pro would deserve a stage all to itself. I do hope it's true though, I'm desperate for a new iPad.
not all that much depending on what exactly they need to announce. The two phones might just be identical except for size so that's easy enough to cover in 30-40 minutes. Same with the 3 iPads (if there are three). 10 minutes to talk about the new Apple Stylus that you can buy to use with any ios device. That leaves the Apple TV and any kind of validation etc system. might be tight to cover in 90 minutes but as its their event if they want to push it to 2 hours they will