A game has "Gone Gold" when the final master copy has been produced at the developer and sent off for replication, packaging and shipment. The game is not yet released, but it will typically be around 2-3 weeks (sometimes less) before it begins appearing on store shelves and online pre-orders arriving at doorsteps. The term itself comes from the old practice of recordable CDs being manufactured with gold film. Hence the gold colored CD actually being the source, with no reference to copies sold as in the recording industry.
"The newest release in that game series is in 2 weeks, it has just Gone Gold!"