I think Wii Sports 2 would be a little bit of a cop-out.
You mean Wii Sports 3, right? Wii Sports Resort is basically "Wii Sports 2". And I really really hate the term "hardcore / core gamer". It's a meaningless label that was perpetuated by the gaming media to differentiate us from casual gamers.
I'm a mainstream gamer, yet I love Wii Sports and WS Resort. I enjoy the Wii Sports games for their simplicity and charm, just like I enjoy Super Mario games for their hop-n-bop action, Metroid for it's sense of isolation on a desolate planet, Zelda for it's adventure and dungeons, etc.
Agree, but I don't think a Wii Sports title will be used to launch Wii U, they will want something that takes advantage of the new Umote, which would not work well at all for a Wii Sports title. I think it is going to be a more traditional title that will use the Umote in a way they feel enhances the title. People can say what they want about Wii Sports, but it was an important title to showcase what Wii could potentially do, kind of like SM64 was used to showcase how the analog stick would change things. The Wii U needs to have something similar, whether it be a casual game (I doubt it) or a more traditional title.
Also note I don't think of casual gaming as something bad, I just think of it as more as a reference to a game that is more "Pick up and play for short bursts" especially with other people.