I have not tried what Ivan said, but as you are on version 2.9.0 I don't think you can because cordova 2.9.0 wasn't installed on the system, just downloaded, and there is no direct update from 2.9.X to 3.X.X.
What I did when upgraded from 2.9.1 to 3.6.4 was, I generated the cordova-3.6.4.jar, deleted cordova-2.9.1.jar from the android project, added cordova-3.6.4.jar and tested, as 2.9.1 included all the plugins in the core and cordova 3.X.X didn't include them, I had to install the plugins I was using with plugman. So, updating like I mentioned, you can generate the .jar for any cordova version and just test it, but your project won't be a real cordova project and you'll need to update everytime like this, and install the plugins using plugman instead of using the cordova CLI So, the other choice you have is to create a new project using the CLI, copy your current html, css and javascript and try. If you were using any plugin it wont work, so you install the plugins you need using the cordova CLI and then you will be able to update easily on new cordova updates.
