We still need to wrap up Savathun's story.
So I imagine The Taken Queen is happening next September to wrap up D2. With D3 to follow in 2021.
Do you really think they're going to wrap up Savathun the same way they wrapped up Oryx? IMO the whole reason she is an interesting villain is because shes too smart to challenge our Guardian(s) directly, and continues to poke at the major conflicts from the sidelines.
I can imagine a situation where we kill Quria and Mara outmaneuvers her, but Savathun has been built up to be too cunning to ever make herself directly vulnerable.
Even Toland says: "You will never meet the deceiver."
also:
"The curse itself is how the deceiver manifests. She has learned from her brother's death. Clever girl, clever girl..."
"Quria is the key. The Mind simulates Oryx, and thereby masters the power to Take. But of course, Quria is no power unto itself."