This is the last time we'll bug you about this, but your account has been dormant for a while, and if you want to preserve your existing username, you just need to let us know sometime in the next 24 hours. It's easy: Hit this button:
Again, even if you don't choose to keep your current name, all of your content will still be there. The only thing that will happen is that a suffix will be added to your current username. You can come back and change it whenever you like.