I wish you would of posted this 3 days ago. It was the deal of the day at cowboom.com $99 used. All the killer deals seem to have expired.

The Nintendo store on eBay is selling that bundle and with the same price as Walmart:

http://www.ebay.com/itm/Wii-U-HW-32GB-Mario-Kart-8-DLC-Bundle-NEW-FREE-SHIPPING-/111822783993?hash=item1a092845f9:g:yxAAAOSwHPlWesux

If $300 is no big deal to you and you'd be happy with the library even if there wasn't another game released for it other than Zelda .... sure go for it. There's fun to be had with it just like any other Nintendo system and there's a lot of Wii and Virtual Console games to play as well that I'm sure will go well with your 4-year-old. Honestly I'm not sure he'll be all that great at Splatoon though, I'd say that's more of a game for somewhat older kids (and beyond). 

But know what you're getting into. There is a high probability that Nintendo has basically stopped major support of this system and is moving on to the NX. If third parties have dev kits that means Nintendo's in-house developers have likely had them for a long time. Given your son is 4-year-old, I think this is more than enough game system for him probably until he's 7/8 then he will start asking for a new system, but I guess that comes with the territory of having kids. 

Since it's for a 4-year-old, like I said I'd probably lean towards "yes", but I would try hard to see if you find a discounted Wii U somewhere or refurbished one from Nintendo for like $199.99. 

https://store.nintendo.com/ng3/browse/productDetailColorSizePicker.jsp?productId=prod150200

$199.99 w/Nintendo Land and 32GB is not bad and it's from Nintendo so I believe it has a full warranty (most of the Nintendo refurb units from what I understand are basically brand new, they're like deadstock inventory). 

I'd get that and then maybe grab Mario Kart 8. I think Splatoon might be too intense for a 4-year-old. Nintendo Land actually is quite a bit of fun with kids. 

If you're still kinda iffy ... I might think a Wii might be a decent stop-gap choice. You could probably get one for $40-$50 and Mario Kart Wii and New Super Mario Bros. Wii and Punch-Out! are dirt cheap (things a 4-year-old could probably play easily). 

I say go for it. It has plenty of great games, backwards compatibility with plenty of great Wii games, and it's January, so you could say Santa's elves misplaced it. XD

No point in waiting for the NX unless you're willing to get it when it comes out, Even if the thing has backwards compatibility, it likely won't have anything worth owning for at least another year. Also, given the success of Splatoon and how short lived the Wii U will have been at this point, I doubt it's online services are going away any time soon. And as it pertains to Splatoon, don't be afraid about letting your kid play. It's incredibly difficult for anyone to bully anyone on there, with its complete lack of in-game communication beyond some preset phrases.

Thank you guys for the awesome responses!! I feel a little better.. Everyone made great points for both ends. The one I like most is to wait and see if after NX is announced/priced/launched see if Wii U might get a price cut to clear the inventory... Then again if I find a good bundle for $199 or $249 I'm gonna have to pull the trigger. I'll post pictures of the game/console when it happens (:

Go get it. It is a good console and good for bonding moments with your kid as well. She likes Splatoon, and SMM. There is/was a $300 bundle with Smash and Splatoon, try to look for it, if it is still available. Not sure if the price increased though.

Playstation has more retail exclusives than the X1 and both have countless more multiplat games not available on WiiU.  Troll harder. =P

To OP:  Get it.  It has good games.  If your kid has not played them they are new to him.