<p>"So Nikon -> Canon -> Nikon -> Canon? "</p>
<p>For 33 years I supported my family and myself as a photographer for the two largest newspapers in Texas, both among the half dozen largest in the USA. When I embarked on that career I decided to use the best tools available to get the job done. During the film era that was Nikon for SLRs and RF Leicas. When my paper went digital, the Nikon shooters were issued first the D1 and then the D2 series, Canon shooters got the current Canon 1D cameras. Due to staffing changes and budget options, after a year with the D2H & D2X bodies, I had the opportunity to change to Canon 1D Mk IIn bodies. For me that was a huge improvement, and a no brainer. Knowing I was going to retire at the end of 2008 I weighed my options, the Nikon D3 was again a no brainer for me, even though I was an early adopter of the original 5D. After using a 5D and D40 from early 2007 to mid-2008 for most assignments and the aging Mk IIn bodies for sports, it was obvious in mid-2008 when I contemplated freelance work after retirement, that the D3 was best for me. Then the D700 and battery packs (with D3 batteries) became even better. The D700 bodies carried me through mid-2013. When it was obvious that Nikon was not going to update the D700 with another actual prosumer camera, and the 5D3 was the real deal, not like the 1D Mk III that badly hurt Canon's reputation, begrudgingly I invested in a pair of 5D3 bodies.<br>
Given Nikon's most recent offerings of a potential prosumer camera: D600, D610, Df and D750, my opinion is Nikon does not want to threaten flagship sales be it the D3S, D4 or D4 successor, with a true successor to the D700. Fortunately for me and a plethora of students, wedding shooters and those who can't or won't justify the 1DX, Canon updated the 5D2 with the 5D3 and now there are rumors of a 5D4.<br>
I still love my old Nikkors and have yet to dispose of my D700s (haven't touched them in more than a year now). It pains me to consider them and a D700 knowing how much better is the 5D3 for what I shoot. I've looked at the Df and thought if only it could do 8 fps, or even 7 fps. I have absolutely no use for either a D600 or D610 and don't consider the D750 as any rival to the 5D3. I've actually used my long Nikkors with Rayqual adapters on my 5D3 bodies. While the images are excellent, losing their AF, auto aperture and EXIF data with the 5D3 is one step forward and two or more steps backwards.<br>
A long answer to a short question.</p>