Great OP. I have to agree with the majority. I may disagree with a few points here and there, it is nothing to go start pulling straws over.
Honestly, all this "Doomzed" stuff is getting old. Neither Nintendo, Microsoft, Sony, Apple or Google have the ability or talent to release a single product to take one of their competitors out of the market entirely. The best they can do is siphon consumers away like a leech and over time bleed one of the others dry to the point where they are not able to compete like they used to. We have not seen this yet.
Most would point to the collapse of Sega and the Dreamcast. Well, there were a number of failures on Sega's part before they collapsed. The Dreamcast was years ahead of it's time and is a great console, but it had to pay for the failures before it (Sega Saturn and Sega CD) along with not being able to sell itself doomed Sega.
Sega's collapse was just as much the product of years of bad decisionmaking from upper management in Sega as it was the onslaught of Sony and Nintendo's competition.
TL;DR: Nintendo is fine. No video game company can single-handedly take out another. The collapse of Sega was just as much the fault of Sega as it was the competition.