Well the thing is he didn't know the direction of Canon developments.
How would that even had been possible to know?
After all, it is for sure at some point "even" Canon extends DR - and that is not because of "whiners" but because it is part of sensor IQ. Would be utterly absurd to think Canon itself don't know this - they optimize the way they think it is most profitable for shareholders and they haven't been wrong this far.
You're correct. Thus far, Canon has chosen not to substantially increased low ISO DR. Their market share has seemingly not suffered for it. Nikon did choose to increase DR, and their market share has not increased. What does that say about the importance of DR to the majority of buyers?
As for jrista spending $25K on his kit not knowing the direction of Canon's developments, consider that he spent half of that total amount less than a year ago, buying a 600 II. After 4-5 years of Canon not increasing low ISO DR, it would be somewhat foolish to assume they would do the opposite the next year...and Jon isn't foolish. In fact, since the 5DIII had been out for a long time, the assumption was easily testable in the case of that camera before committing to a purchase.
Plus, many of stick to a system in the long run, knowing full well that technology runs in cycles. For the last several years Canon has put a lot more effort into AF than IQ... now they have industry leading AF and industry trailing IQ..... where do you think the research effort will now be directed? It is logical to expect that at some time soon we will see a Canon with better IQ. I think that's why there is so much interest in the 7D2... many hope that this will be the point where new tech emerges...
Who knows... maybe five years down the road we will be bragging about Canon's IQ and lamenting the poor AF... nobody knows what the future will bring, but there is one sure bet... no camera or manufacturer will ever produce a model that is the best at everything.