The answer to this question is that it has an insignificant effect either way.

Thats what Im considering.  Nintendo fans, Smash fans know everything about the game.  But the expanded audience, and other

potential gamers, including from the PS4 and XB1, might think, its not worth buying a WiiU for a game that looks to be more

fun with a group of friends.   People have always said Smash is a game you play with friends together.  

I've seen Smash4 rise up in Amazon, but are we seeing a direct effect on WiiU sales yet?

Well, then the guy needs to buy 8 controllers so... In a way... Nintendo is still get a lot of money! But either ways, I doubt thats the reason. The wii had a ton of local multiplayer games but that didnt stop it from selling

I always suspected as such, because that's why my friends usually opt out of getting Nintendo consoles. They love Smash, Kart and Zelda, so they usually come over for multi-player and torrent the Zelda (or Mario) games that are single-player onto their PC's. Cheap bastards.

Well I dont know about other people but I was visiting a colleague and brought my WiiU and Mario Kart8 we were 6 people ate pizza and played the game (obviously not all people at the same time) and in the end 1 guy bought a WiiU the next day because he wanted to play MK all the time and not just when I was bringing my equipment :) or invited them.

So the local multiplayer  gave him a few hours to try the game made him realize he loves it and since he can play with alot of people that dont own a console as long as they visit him he just went and bought a WiiU including MK8.

Where I live party games are quite popular  everyone had a Wii just for parties. Smash might make WiiU a party console.

when i played my best friend at golden eye for the 1st time i went home thinking "there's no way i'll ever beat him unless i buy the game". Pretty sure that would be alot of people's mantality here.

People would still play their friend's Wii U even if only 4 players was still the max. I personally love the 8 player battles and with it Nintendo does have a chance to sell a lot more adapters and controllers.

There is a thread asking if Nintendo cares about install base numbers, and 

Jizz_Beard_thePirate  pointed out that even if gamers dont by WiiU for Smash,

owners of the game and console will probably look into buying extra controllers for the game anyway. 

So Nintendo profits.   Not to forget Smash is helping to sell Amiibos.  So, 

It looks like Nintendo cares more that the existing install base spends money than bragging rights

to the biggest install base.  Games like Smash and Mariokart do boost consoles sales, but more importantly

they ensure that owners keep spending money in the form of DLC, controllers, figurines, etc.

wow

ok

Not so much that it'll make a noteworthy difference anyway. It would've had 4 player anyway, so I doubt 8 player is gonna make difference, unless more than 3 friends decide that they want to play Smash at the exact same time.