As I do every few days, I was looking for Digimon Survive information once again today, and for a change, I found some! About two days ago, Toei Animations released their financial report for the last fiscal year, in which they shared their company growth, sales, brand reach, and much more with their investors. In addition, they also released their roadmap for the coming year in this document - and among them, Digimon Survive's planned release date!
As it stands (and according to this document - see page 14 or the image below), Digimon Survive is scheduled for Fall 2021!
This release timeframe does line up perfectly with the upcoming DigiFes 2021 or E3 should they plan on announcing its release date soon.