Predictions based in the invite (the fact that this is all about an iWatch is assumed):
1. iWatch will be round, not square, as indicated by the abundance of curves in the background image
2. iWatch will come in two colors: white and grey, as indicated by the colors in the background
3. iWatch will support tactile feedback, as indicated by the raised apple logo (not to mention a recent patent granted to Apple for this very feature)
4. iWatch will support voice recognition and natural language processing (a.k.a., Siri v.next), as indicated by "we could say"
6. iWatch will support voice synthesis, not really indicated by the invite, but follows along with wanting to make a complete experience
7. iWatch slaves to, or integrates with, nearby iDevices, as indicated by "...more" seeming to imply that this is intended to be a complementary device, not necessarily a primary or stand-alone experience (might be functional that way, but really intended to be part of an ecosystem)
8. iWatch will have a development platform and partners will show specific demos for given verticals showing what what we might be able to "Wish..." for.
9. The iWatch will be available internationally at launch, as indicated by the locale-neutral date "9/9", doesn't make what country you live in, that date is always going to be understood
10. iWatch will support remote media control for media running on a nearby iDevice, as indicated by the choice of venue for the announcement, a theater, not a convention center
11. To get the most out of the iWatch you will also have to have an iPhone 6, as indicated by the two parts of the Apple logo -- a large part, and a small part -- that are prominent in the background, and that the smaller part is the one casting the sundial shadow. Better free up more space on those credit cards folks.
12. Apple will pretend that they invented the idea of a "smart watch" and that nothing like what you will see on 9/9 has ever been seen before, despite numerous products from other companies that are already on the market.
Seriously, I have thought for some time that Apple has done an extremely poor job of capitalizing on the localized Apple ecosystems that are created when a fanboi just has to have the newest [iDevice].
They've basically had a captive audience of millions who have drunk the koolaid, and to put it quite bluntly, they have done absolutely nothing to make the experience when you have a MacBook Pro, iPhone, iPad (and iWatch) in proximity to each other special in any way. When you have complete control over the local ecosystem like that something...magical...should happen.

Yet iUsers interact with their iDevices in much the same way that PC users interact with theirs.
I'm not a huge Apple fan, but I do hope they show some sign of thinking about creating a seamless, integrated experience when they own the iUser.