There wasn't even a need for sequels as those games are still selling strong today. Nintendo should've continued to release new disrupting games. An RPG that focuses on local multiplayer and co-op featuring Mii's would have been the best thing on earth. We're regularly having gaming parties here and everyone has been craving for such a game. A full blown Karaoke game made by Nintendo would've filled a big void as well. "We Sing" is selling quite well in Europe but it can't compete with Nintendo quality. And of course New Legend of Zelda.
I disagree with the reasoning that sequels shouldn't be made, if the previous game(s) still sell(s). After all, that kind of logic would restrict us to only one Super Mario Bros. game per system. Nintendo didn't make a Wii Motion Plus tennis, so that alone would justify Wii Sports 3. Sequels are necessary to hold on to customers and if you look at the HD consoles, that's basically all that is done on them. Nowadays virtually every new release has a number attached to it.
I wholeheartedly agree on new IPs though which I briefly mentioned as another option in a previous post.