This looks very fishy to me. It looks more like someone's pipe dream and less like something from MS, IMHO.
"Onboard wake button (use as unattached clipboard)"? That is odd wording. What is an "onboard wake button" and what does it have to do with detaching the clipboard? "MicroSD Explanation slot"? Uh-uh. That should be "expansion". 9 hour clipboard battery life? HA! This alone is reason to believe that this is fake. Lots of people want something like this, but I just don't see it. Reference to Type Covers? No hinge design reference? That's the Surface Pro line. People have suggested that MS should hybrid the two lines, but I really doubt they'd be doing it already and probably would not present it like this. The language & terminology is all wrong (even for a leak). And October for a release... I highly doubt it with redstone 2 being pushed off til early next year and the more probable launch of a Surface Phone this year.
This looks more like someone trying to hybrid the SP4 and the SB into one machine with perfect non-niche specs. While I may be proven wrong, I sincerely doubt that this is a leak at all, and it's just someone's cool idea of what they want to see in a next-gen Surface Book. Personally, I just want to see the next gen unit get all the bugs worked out of the first one before they try any of this.