The Gamecube sold abysmally. Sitting just around 20 million, it's Nintendo's biggest failure sans Virtual boy. Yet I would argue that it was Nintendo's greatest system. Sporting a comfortable controller, the best Nintendo first party since the SNES, some great third party, and all of these games looked amazing because of the powerful hardware. The Gamecube was without a doubt a "Core" gamers console. 

I think that the reason it failed wasn't because of what it was, but simply becuase of the PS2. I don't think we will ever see a force as dominant as that console out of the big three again. I think the market is much bigger now, and more open minded to owning two or more consoles. 

So here is my scenario. The Wii lifecycle is completed, Nintendo announces a console with specs on par, or slightly better than PS4 Nextbox, normal controller, updated Wii mote, great online services, and a bevvy of First party and third party support. 

How would it sell? Would it recieve third party support? How would it be viewed. 

I think that in a market where there is no PS2 equivilent, the GCN2 could outsell it's competitors. Nintendo already has a lot of families buying the system for Mario, regardless of what control scheme/power. So they have that crowd locked up. Then let's se they gain 10-15 million core gamers that are open minded, their typical 20-25 million core fanbase, and another 10 or so million for the casuals. 

I think that a GCN2 would succeed.

Only if they change up the design. If I was a 13 year old I wouldn't be caught dead with a "cute" design system like that. If I was an adult I would say it belonged to one of my kids.

I'm talking more about power wise, and philosophy wise. Not really about the Gamecube itself. 

It would probably sell slightly more than the Gamecube 1, at the cost of losing the entire casual support.

If it launced with an updated Wii Mote bundled, and NSMB I think the casuals would be appeased. Nintendo would simply push them to the back of the crowd like they did to their fans with the Wii.

Don't forget, a lot of those 150 mil hd twin userbase are Ninty fans getting their HD console fix (ahem, like myself) so yes for many, GC2 would be their ultimate console.

GC2 would succeed b/c the momentum is different. N64 was behind in times/uncool, sony was just too hot at the with their brand power, that affected gamecube. But now a GC2 would've been really popular b/c of the Wii name behind nintendo. Just for marketing purposes, the Wii U name despite being dumb as shit, would have sold as long as the POWER was there. Most people would just call it "nintendo" anyway lol. but oh well, I guess Nintendo is satisfied being the 2nd or part of a multi console household.

With Nintendos third party support, they would've been crushed this gen if the Gamecube had taken the Wii's place. Nintendo learned their lesson...and their place belongs with families and casuals. The sales proved it.

Nintendo isnt about satisfying adults themelves, its mainly marketed towards kids and families. If you dont like have liked what Nintendo has offered for years, it really shouldn't matter what the console looks like.

If you had read the OP you would have seen that replacing the Wii was not what I was suggesting, but you are content to come in give your typical "Nintendo is for babies" comment and leave. 

Nintendo is about satisfying the people who enjoy their games, whether it be adults or kids.