I don't think Lightning headphones are headed our way before the fall (where by "headed our way", I am referencing the elimination of the mini jack, which is long over due, IMO).
I think that you can head down to your local Apple Store/reseller and have a good look at the iPad Pro. Reduce that screen size, and you'll know what Apple is going to show us in a week-ish. I don't think any rocket science is necessary for this one.
Same with iPhone 6se (or whatever they call it). Have a good look at the 6s, scale it down, and BAM!
Apple Watch 2 (if they talk about that) is the same. Take the current Watch and shave off a few mili-things and that's it. Big whoop!
If anyone is getting excited that Apple is gonna go all iThing Revolution™ at this show, they are mistaken. Other than caving in and adding ports for all sorts of "I need to connect my 18TB RAID 5 to my iPad" cravings, I don't think you're going to see anything you can't already see at the local dealer. There will just be smaller versions of those things.
Personally, if I were a member of the media, there's no way I'd fork over the travel bucks for this event.
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On that note, there is a possibility in the software side of things that may be revealed within the invite. Apple has long added those fancy little codes in the invitation message, and this year the word "loop" appears. I have heard many people talking about this as a reference to One Infinite Loop since the event is being held at the Apple campus. Could the word "loop" involve something more … interesting? Are there not "loops" in programs like Aperture and Lightroom? Are there not "loops" in Garageband?
I'm probably reading too much into it, considering Apple hasn't really had a good code in a while. But, still …
Something worth arguing about (or not).