Reader Raffi sent us this video he shot from a holiday party where a developer for Natal was playing Geometry Wars with just hand gestures. We can't say for sure if this is really a Natal powered game of Geometry Wars until Microsoft says it is, but it's no secret that Natal developers are experimenting to incorporate Natal controls into a wide assortment of games.
This doesn't confirm that a Geometry Wars powered Natal game will ever come out, but it does show us that even twin stick shooters are potentially possible on Natal. Using motion controls to play any sort of shoot 'em up, however, doesn't sound like such a good idea.
By the way, if you like the song in the video, you can download it from here for free.