The problem with a Wii Sports 2 is that it won't be a pack in game. The reality is that no game on Wii will surpass the install base of Wii Sports. Not Brawl, Not Wii Fit, not any game. Simply because EVERY damn Wii comes with Wii Sports.
Nintendo could maybe pull a rabbit out of its a$$ and provide online for Wii Sports with a future firmware update. But it will be highly challenging since they didn't add online initially. I could only dream.