Based on the stars alignment and the moon phase, I am now 75% confident about a Nikon announcement during the second week of October. Expected is a Nikon D3 refresh (probably called Nikon D3s – not sure yet) and at least a Nikon AF-S Nikkor 16-35mm f/4G ED VR lens.
I expect the official press invitations to be sent out next week – Nikon usually sends them a week or two before the actual press conference.