Pretty sure that all the people who are so much against mouse support have never really used the iPad Pro with the keyboard for an extended period of time, doing work that is not related to art.
Once apple introduced the keyboard and is so heavily marketing the iPad Pro with the keyboard, it must also introduce some sort of touchpad or mouse support. Working on the iPad for more than one hour while it is docked to the keybaord, having to reach out and touch the screen for everything is just not ergonomic and is causing causing arm fatigue / pain.
This is exactly why apple never created a touchscreen Mac, because reaching out to touch the screen while sitting in a desk is just uncomfortable and unproductive (at least according to quotes I have seen from Steve Job).
So instead of creating a touchscreen Mac, they went ahead and created the the docked iPad
I understand that the iPad is a touch first device and that works great when we are holding it in our hands. When docked to the keyboard however it's just uncomfortable having to reach out and touch the screen for everything, specifically on the bigger 12.9 model.
People are are so much against Mouse / Touchpad support have probably never used a 2in1 Chromebook with android apps. The Keyboard and mouse work great with them, and so does touch in tablet mode.
They have also probably never used an Android tablet with a mouse and keyboard. It also works very well when you would like to be more productive.
I agree with other posters that Mouse support is probably coming, but I assume it will be an Apple iPad specific mouse or touchpad and they will charge extra for it...