Even if Nintendo were to come out with this über-powerful console, it's still practically impossible to kill off Xbox and PlayStation just like that.

It will either be Sony or Ninty in first or second. I don't think either of them will get their past consoles beast like sales.

Yes, they'll just share a smaller piece of the pie

the loser of the next gen will go away as long as its not nintendo m$ shareholder would be mad if the xbox69 woul just sale 20m ltd. and sony would just go belly up if the ps5 flops. nintendo cant go awy bcause they have nothing to go to, and they can survive with less sales than sony.

The entire 7th gen proves your main argument wrong, OP. It is true that one should not underestimate Nintendo, especially now that they've shown actual will and effort towards changing for the future, but the opposite is also true; you should never overestimate them either.

What is a comeback though? As in, a financial comeback? Or as in appealing to the same market as its two main competitors?
Because if the latter, I don't think they have it in them. They're too out of touch of the times. They have their devoted fan base, and there's not a thing under the sun they can do to shake them off, but I have huge doubts as to their ability to attract new customers.
Nintendo's days are numbered and it sucks.

Nintendo won't make a huge comeback. They'll never have a truly succesful home console again.

"Not everyone wants to play games like mario or zelda, a lot of people rather look for more mature looking exclusives."

1. Nintendo has much more than mario and zelda.

2. Debates on what "mature looking" means aside, wouldn't a nintendo system with 3rd parties get those anyway?

"So nintendo getting third parties doesnt gurrentee dominance, see the gamecube."

I can't believe you wrote that. The gamecube didn't "get third parties". It sure had considerably more than N64, but still missed on the most important 3rd party games of the gen. And check the market context first: The gamecube released when ps2 had already established itself. From there won, it was impossible to gain enough ground.

A nintendo system that gets fair treatment from third parties would force sony and ms out after one generation or 2 because it would have nintendo exclusives + 99% of the competitors library.

I believe so. Sony and Microsoft just are not going to concede that easily.

I don't think this is true.  People do want to play these games, they are just not inclined anymore to pay for a console to ONLY play these games, where they might have done in the past.  The Wii U right now (and I've never owned one) has perhaps 4 or 5 games I'd love to play, and maybe 1 or 2 in the pipeline.  But thats over a near 3 year period.  Its just not enough to justify spending on a console.  

Thats the problem.  The Wii U might have 1 or 2 games per year that are the absolute pinnacle of gaming, but thats all it has.  There is literally nothing in between and no 3rd party support.  So the average gamer will just shrug their shoulders and sacrifice buying the Wii U at all.