Seems like almost a consensus that Apple's September 7th event is not going to feature updates to the Mac lineup or a launch of any new Apple display.
Jim Dalrymple via theloop seem to be the first to make the prediction:
I agree completely that there has to be updates coming for various products in the Mac lineup at some point, but September just doesn’t seem right to me. Assuming Apple keeps September as its iPhone event, as its done over the past few years, the company will want to keep the focus on iPhone and nothing else.
If there is a distraction, it would be for the release of iOS, which is complementary to the iPhone. Macs don’t fit in there at all. One of two things would happen: Either the Macs would take away from the importance of the iPhone release, or the Macs would get ignored completely. Neither one of those scenarios are good for Apple or the Mac products.
Add now to that Rene Ritchie in his iMore preview of the event, Mark Gruman of Bloomberg on what type of updates they could be working on, and Jason Snell on Six Colors explaining how Apple has handle these things in the past - it seems pretty likely we won't be getting updates to the Mac lineup or a 5k Display.
I tend to agree with Jim, especially now after seeing the event image, that this is all about iPhone. Even if the iPhone shares a stage with an Apple Watch 2 update, the device is essentially an accessory of iPhone. That's not to put down the beautiful of the Apple Watch but more to recognize that it is an up sale to iPhone customers and therefore showing off iOS 10 and watchOS 3 together on new devices makes sense. macOS on new iMacs or showing some new "Dynamic Function Row" on thiner MacBook Pros is too much for one event and would take away from iPhone. Worse it force them into an abbreviated version of all the updates smashed into one event. Now can you imagine a new display announcement on top of that?
I think they separate them out and do a smaller event in late October. If the displays are ready then they pair perfectly with the MacBook Pro updates similar to the Apple Watch and iPhone.