In a tweet (shown below), came a new key visual for the upcoming series Digimon Adventure Tri. As a direct second sequel to the original series that aired back in 1999, Digimon Adventure Tri is set to air in the anime Spring 2015 season.
— デジモンアドベンチャー tri. 公式 (@Digi_advntr15th) March 10, 2015
For those who missed it, below is the video that was released about the project from Toei Animation:
And here is how the plot has been described so far:
The series is set approximately six years after the events of Digimon Adventure, three years after Digimon Adventure 02. Taichi Yagami is now 17 and attending high school, when he and his friends, the Chosen Children group who saved the Digital World in August 1999, reunite with their Digimon partners to once more protect the Digital World from evil. Courtesy of Wikipedia