Android Cupcake will go out May 11th.

BGR Reports the image above, yay! Android update 1.5 Cupcake will be available to all of the G1 owners via over-the-air (OTA) updates. We have been waiting for a while for this to finally come out... now all you have to do is wait.

The OTA update will start going out May 11th till the end of the month. It should look similar to this;