I'm not sure that has to be any early demise of the format. There are too many assumptions that are being made that seem to be bit off.
Formats in the film days were necessary for the manufacture of cameras for film developing. That isn't the case now. Digital doesn't do developing tanks. The slew of compact cameras use the same imaging chip because it's handy and off the shelf, not because it's necessary.
The idea that consumers buy lenses in droves for their DSLRs is out the window, too. Average camera buyers don't. NR readers might, that accounts for a minuscule part of the worldwide market.
Most people buy a DSLR and a stock lens and 'think' they will expand upon it and never do. Ever.
Nikon will make whatever it thinks will make it money. (Personally, I think the company screwed up with the V/J mirror less simply by not joining the micro 4/3ds community and becoming dominate in that space. I think they were wussies for not wanting to put up and compete. Shame on them.)
As for the SLR market, Canon was in the right market space at the right time for video - and it shows, and and Canon has also enjoyed a price point advantage for sometime, too. Canon is driving some major market space, more than ever, so that the topic question is more than a Nikon question, too.
I have both DX and FX lenses (some so old that they weren't 'FX'), and I 'think' I'll get a D800, but I'm in no hurry (in's that convenient?), then I might mind if DX dies. ;-)