Microsoft has officialy announced today that the Gold Build of Mango is now available. The RTM means that active development is now complete and it has been submitted for carrier testing. It will now be tested on various networks and devices around the world. The official build for the RTM is 7720 and will use the red Windows Theme by default.
The update will be ready for the rest of us this fall, where we can update our devices or get a new device with Mango preinstalled. Other manufacturers like HTC and Samsung will also be releasing devices for the new version of WP.
We can definitely expect to see this update in the September or October. If you are on the fence about getting a Windows Phone, you will want to wait until Mango is released to get one.