The announcement was made through the Nintendo of America Twitter account. Linking to the NES Classic webpage at the end.
#NESClassic Edition will return to stores on June 29! This system and the #SNESClassic Edition system are expected to be available through the end of the year.
Like before, the NES Classic Edition will cost $59.99. The games available are also exactly the same as before, ranging from Super Mario to Ninja Gaiden. The full list of games can be found on the official website.
Production of the Classic Edition stopped only months after the product had launched. Due to extreme demand, the limited supplies ran out instantaneously, as did any later shipments. Nintendo responded to the heavy consumer frustrations with a promise to start production back up the following summer (that's now).
The exclusivity of the NES Classic caused a massive spike in hardware scalpers, who are currently selling the device for $200+. The SNES Classic Edition did not suffer from the same level of rarity as the first mini console. Though it has also seen mild price inflation.