The surprise factor is less and less at Apple and it is that each article that the company is going to present, lately ends up filtered through different images on the web. I refer to this since the FCC has leaked some sketches of what the Magic Mouse 2 and the new Wireless Bluetooth Keyboard from Apple may be.
If we look closely and as you can see in the images that accompany this post, you can see a silkscreen in which the number and type of Magic Mouse model is indicated. Even so, unfortunately the images do not show the final design or relevant details so that we can get an idea of what is new they are going to incorporate, the only thing that is known is that they will incorporate the Bluetooth 4.2 low consumption protocol.
The current Apple keyboard and Magic Mouse use the Bluetooth 2.0 standard, so this update to 4.2 is a significant improvement. According to your specifications, Bluetooth 4.2 is faster, safer, and more efficient energetically speaking. Also from what I have been able to deduce regarding these sketches is that for example the new Magic Mouse seems to have an integrated battery, so the change of batteries in the mouse may have come to an end.
On the other hand on September 9 Apple already has the keynote programmed to introduce the new iPhones, iPad Mini, and probably the new Apple TV. Perhaps these new accessories will also make their appearance on the Apple website on the same day of the presentation.
However, since these new input devices are not relevant beyond simple accessories, they may simply are put up for sale at any time without notice and without a keynote in between. Without going any further, yesterday Apple put on sale different extension kits for Apple Watch bands without prior promotion.