Well it is not quite the definitive leak but it seems the source code of October 6 Event page has “Lumia, Surface, Band, Windows Phone” in the keywords. A strong hint of what may be the content of the event in terms of Lumia, Surface and Band announcements. All these categories are unique and so having them in keyword most probably means Lumia 950 & Lumia 950 XL, Surface Pro 4 and Microsoft Band 2 announcements. All these devices have been rumored and leaked repeatedly to this date.
Also interesting is the “Windows Announcement” keyword. So may be something Windows 10’s official TH2 update related or may be Windows 10 Mobile becomes official on this date.