It would be interesting to know why the F6 has been discontinued. I would doubt that the costs of continued production would make the camera uneconomic for Nikon. True, dozens of these cameras are for sale sale used, but a slow trickle of new cameras would continue to serve those who want to buy new...
Isn't it obvious? At some point, every product comes to the end of its life cycle. If there were enough sales to generate profit we would have an F7 on the shelves since February this year, with the F6 slowly phasing out. However, kids picking up film photography are not willing to spend a big buck on a brand new pro camera so there you have it. I'm sure, though, we'll be fed by "facts" and theories by "industry experts" in no time.