According to the official twitter account for Windows Phone, Microsoft has shipped Windows Phone 7 to handset makers. We take this as possibly reaching gold status for the OS.
UPDATE: Windows Team Blog has been updated and indeed Windows Phone 7 has gone RTM (released to manufacturing).
Windows Phone 7 is the most thoroughly tested mobile platform Microsoft has ever released. We had nearly ten thousand devices running automated tests daily, over a half million hours of active self-hosting use, over three and a half million hours of stress test passes, and eight and a half million hours of fully automated test passes. We’ve had thousands of independent software vendors and early adopters testing our software and giving us great feedback. We are ready.
Windows Phone 7 has shipped to handset makers, then to stores near you this holiday season! http://ow.ly/2y7ot #wp7
There you have it folks. RTM. Done. Next stop actual Windows Phone 7 devices hitting stores before the holiday season.