Should I buy Kinect for my Xbox 360 or Wait until Xbox 720?!?

I Was Watching the E3 Previews for the New Kinect Games, Such as Forza Motorsport 4 and Ghost Recon: Future Soldier, and the New Xbox Screens that you Can Controll with Kinect. I Really Want Kinect Now, for All the New Games and it Seems Pretty Revolutionary and a Must Have, but I Don't Want to Spend Over 100 Bucks and then have to Throw it Away Shortly and Buy a New One for Xbox 720. This Scares Me Because Xbox 720 Was Supposed to Come Out Over a Year Ago, and Should Be Here Really Soon... What's Everyone Else Doing about It?!