Dude, you couldn't be any more wrong. Sony and MS would drop out of gaming long before Nintendo goes 3rd party. Let's take an objective look at each of the big 3's position as it stands right now.
Sony: If PS4 hadn't been successful that may have very well been the case for Sony. They lost all the money they made on the first 2 Playstations with the PS3. Think about that, because those are two very successful consoles, the second still ranking as the best selling gaming device in history iirc and they lost it all.
Microsoft: Microsoft has never made any profit from the XBox brand. When you have Windows money that's to be expected but with the original Xbox being only a minimal success and the high failure rate of the 360 they may have actually lost money. The XBox One didn't perform up to expectations either.
Now we come to Nintendo. Sure they only make games, but their games are household names and instantly recognizable. Nintendo has a trend of being conservative. Even when their consoles don't light the world on fire in terms of sales, they recoup their costs in software sales. People like to pretend Nintendo is on its deathbed in the coma ward and all that's needed is to pull the plug and that's it. That's a fantasy fabricated by the gaming media.
The Wii was one of the most successful gaming machines of all time. They made crazy money on that thing. And that was alongside the original DS which was also a monster in moving hardware. The DS is the best selling handheld of all time and the 2nd best gaming device of all time behind PS2 iirc. So we're less than 10 years removed from Nintendo having their 2 biggest successes in company history, yet people are doomsaying more than ever. The 3DS is a consistent seller. Wii U was a failure in terms of hardware sales but was untouchable in terms of exclusive software sales. More than 5 exclusive games on Wii U have sold over 5 million units. PS4 and XBox One don't have that (or at least didn't at the end of Wii U's life cycle which is the last time I checked).
Now they rise from the ashes of the Wii U like a phoenix with the Switch. It's quickly become the fastest selling gaming device in history in less than a year on the market and people are still doomsaying? Nintendo is King. Even when they're down, they're never out. If the success of the Switch doesn't teach people to never count Nintendo out, nothing will.