What most people who invent specs don't realize is if the D4 was already intended to be released in time for London 2012 then it is already pretty much feature-complete by the time Canon announced the 1Dx, that's why they pre-announced it 5 months in advance, they already have a good idea what the other guys would be releasing and they know it would be too late to add features at the last minute just to keep up with the competition. And we're not even talking about the effect of the earthquake, tsunami and flooding on Nikon's manufacturing...
And just to correct the historical record, the D90 was rushed to market only because Canon was talking up video for DSLRs a few years before that, thus tipping their 5D2 hand, and Nikon decided to pip them to get the "first video DSLR" tag, even if the specs were obviously rushed and inferior to what the 5D2 would bring a short time later. So maybe they were first to market on paper, but Canon evidently made theirs first in their dev labs, only it took a bit longer to release.