Canon 6D might be of interest to D600 purchasers

It seems that D600 sales have been below stellar. And 6D introduction will put extra pressure. Besides, D800 novelty has worn off and its sales slowed down. The jury is still out but I shall not be surprised if Nikon adds new easily implementable features via a D600 FW upgrade.

Single-button-press full zoom is an important feature for some users and it is trivial to implement in FW. A pure marketing decision on Nikon's part indicative of how much they care about their user base.

Leo