Despite the lack of details, the announcement is pretty clear. NVIDIA will reveal its Ampere-based desktop GPUs via a yet-to-be-specified event on August 31. Presumably, the company will do a public livestream so everyone can see in real-time what all the fuzz is about.
The "21 years" seems a reference to the GeForce 256, which was released in October 1999. The GeForce 256 was marketed as world's first GPU.
...#UltimateCountdown pic.twitter.com/f23HcbHUk6
— NVIDIA GeForce (@NVIDIAGeForce) August 10, 2020