the nikon rumors website claims that no such thing is going to happen but i sometimes wonder if that website is more of an arm of nikon marketing ...
All rumor sites are arms of marketing to some extent. When a rumor site depends on anonymous tips (that's all of them) then the camera companies can manipulate certain rumors. This comes with the territory, and there ain't much that can be done about it.
Both Nikon and Canon Medium Format rumors serve as polls, i.e. would you buy one if it were made. And how better to get Canon/Nikon fans to take the poll than to float a Medium Format Rumor.