Very unlikely, but not impossible: An update on the new Mac Pro
We already know that a new Mac Pro is coming. But it's not the kind of thing that Apple would host a special event to unveil —the company already took the wraps off the round Mac at WWDC this year—so instead it will likely get a special mention at whatever Apple event occurs nearest the big Mac's release.
It wouldn't be crazy to get an update on that Mac next week. But it might get power users so excited that they forget about any iPhone announcements.
A boring near-certainty: A rehash of iOS 7
With iOS 7's release just around the corner, expect an extended rehash of its features. Maybe Apple will announce a minor new feature or two to spice things up, but most likely, the company will simply take the opportunity to remind its captive audience about all of the flagship features that the upcoming version of iOS will contain.
Apple released the beta version of iOS 7 to developers first for the iPhone, and only later for the iPad. Don't be gobsmacked if Apple announces that iOS 7's official release will similarly hit the iPhone first, and the tablet some weeks later. Such an announcement might also mean that new iPads will be coming later this fall.
Simply not going to happen at all: Ballmer to Apple
Outgoing Microsoft CEO Steve Ballmer may be looking for a job, but I'll guarantee you that he's not coming to work at Apple, so no such announcement will be made at Apple's Tuesday event.
Macworld, of course, will have live coverage of Apple's event on September 10.
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