Or what Euphoria said so much more succintly. 

A Wii Sports game would do more than either of those, yet Nintendo seem to be refusing to make one.

I wouldn't expect Wii- type numbers. These new games could have appeal if they are good and if they are promoted properly. But first the Wii U itself needs to be promoted properly. Fit and Party could have an impact as part of the overall family package that Wii U offers, including Zelda, COD, Watch-Dogs, Mario, Just Dance and so on. To really capture the imagination of the casual audience, however, I think a new game with a new concept needs to be made, one that can only be done on Wii U. These games aren't it.

the new Wii Fit does have something new though, that Fit Meter thing. I guess it all depends on how they market it and if they can make the new features catch on.

That said I wouldn't expect the games to sell near their Wii entries. Wii Party could do quite good because of it's nature as a mini-games collection once the user-base has grown a little but Wii Fit is more dependent on trends. One that could have died down. I don't think it'll bomb though, contrary to games like Brain Age and Wii party U for that matter, the Wii Fit experience can't be replicated on smartphones and tablets.

Yes.

Although the number is still questionable. Bringing three casuals to the Wii U would still qualify as "bringing casual gamers."

I'm going to say not really for a number of reasons:

1) WiiU price is still a little high
2) By the time they finally drop they'll have direct competition from XB1 (which is granted even more expensive)
3) Casuals generally don't buy the same game over and over again like Madden and Call of Duty fans do. They'll buy it once, or twice then move on to something 'new' and be happy playing the version they have. And they own these games already.
On Wii it was very common to see steep drops from the first title to the next in a series unless the sequel really added something 'new' (like WM+ in Wii Sports Resort and Tiger Woods)
4) Wii Fit created a fad in the fad centric fitness industry. That fad is long over now (replaced by the dance/exercise games (Zumba/Just Dance/Dance Central) which has also passed the fad stage and are seeing steep declines. It'll take a lot more than a rehash of Wii Fit to entice people to buy it again (especially if they need to buy a whole new system to boot). And really, even I reject the logic of buying a new system for a new Wii Fit and I used Wii Fit/WF+ for over 300 hrs. A Wii Fit that used the added functionality of Wii Motion Plus for a new slew of exercises / better feedback, I would have bought on Wii gladly. Even now. One that uses the gamepad? It does not add anything to a workout (except off TV play). It's not worth $350+. No how.
5) Wii Party U will have less of a hurdle than Wii Fit since party games are eternal but this is not exactly a system seller either and will mainly appeal to casuals who already own a WiiU. I'm sure there's a couple out there.
6) The gamepad. Casual don't want it. They want simply accessible controls like wiimotes/kinect/touch screens not dual analog monstrosities of imputs options. Having to pay $300 for a system they don't want to play a game or two they do want is a hard sell. Especially when they have a version or two of that game already on a system they already own.

What Nintendo needs is a game that introduces NEW/fun/accessible gameplay that only the gamepad can deliver to entice casuals to WiiU. And then these games will have a real chance. Otherwise they'll be like Nintendogs + Cats and Brain Age on 3DS. Mediocore to okay sales but not the hits they were on DS.

It definitely won't reach Wii level sales.

look at the sales of those Wii titles now look at sales of games like Star Fox...thats why you saw no Star Fox and a bunch of Wii titles and quite frankly why you wont see another Star Fox anytime soon. You know whats funny i used to think just like you. I dont anymore, because Ninty not making those WiiGames i dont care about is absoulely NO garauntee that they would make Star Fox, Fzero and so on. You want a world where these titles dont exist, thats selfish, i get it i was their but it is selfish. Personally i would care if we never see any of them again because i find the lot of them mediocore at best, atrocious at worst. But as i said you cant know for sure if those not being made would ensure than Ninty made the games you want to play. This is why i mess with other consoles because i never have to feel my gaming is not being met.

Edit: im just gonna say it, and anyone can call me a fanboy if they want. One of the reasons why I prefer SOny is they seem to take more risks game wise, theyll have games made that they are not to sure will even sell. Ninty doesnt really seem to be like that anyomre, more and more they seem to just stick to what they know sells. I hope they change this attitude in the near future.

if the price for Wii U was 250$ then YES for now I say NO.

one thing I found odd is how nintendogs + cats(3DS) did low numbers compared to nintendogs on DS.