You guys really need to stop being so naive. Why would nintendo NOT make a mario tennis? Its an ongoing title, and its a sports game. Mario Tennis made them thousands of dollars in the past, and thats with no motion sensing. The wii's capabilities make the demand for any and ALL sports games 10x higher.
I can garuntee you (you can even quote me if you like) that their will be wii versions of Mario Tennis, Soccer, Golf, Baseball and many other sports (football (us)?, basketball?).