Given how many times Savathun was referenced within the D2 campaign (Savathun’s Handmaidens, Savathun’s Song, the Herald of Savathun, etc.), it’s fairly likely the messages are being sent back to her. Both of Oryx’s sisters have worms, and Savathun does want the power of the Deep:
Savathûn, Witch-Queen, looks at him with dry wariness. “Is it the sword logic I need to go into the Deep, and take your power for myself?”
The fact that messages are being sent to Oryx’s throne world is a bit strange (is it Oryx’s? I remember a scan saying messages were being sent to the Ascendent Realm, but not to his throne), the Hive do have access to each other’s throne worlds:
And you, Ir Halak, you are a wizard too, as is the way of twins. I have been with Xivu Arath, who complains that you have made a song, and sung it in her throne world, and killed everyone who listened, quite irrevocably. Will we have songs instead of swords and boomers?
Out of love for her brother, which was the same as the desire to kill him, Savathûn leaked a secret to Xivu Arath — ‘listen, Xivu, Oryx’s throne world has been compromised. You can cut your way in from here.’ Xivu Arath used this to plan an ambush.
Her Ketch was adjacent to it when Oryx used his weapon to expand the Dreadnaut’s throne world beyond the confines of the ship itself. The effect devastated most of the awoken(and the rings of Saturn to boot) but Mara has already impregnated her Harbingers on the Dreadnaut. Which should be incubating now. Mara herself is likely recuperating on the Dreadnaut now getting ready to use her harbinger babies to take it over. Become a sort of Awoken Taken Queen.
Two things. One, her Harbingers had no effect whatsoever on Oryx’s Dreadnaught. The other smaller ships, however, were decimated. And two, doesn’t she embrace her death? She didn’t even try to escape unlike Prince Uldren.
Also, doesn’t she summon the Harbingers using those other people as well? If she did survive (doubtful), I don’t think she could have extended that immortality to those other people as well.
Queen Mara Sov could be there, forget all my other reasons (JK still reason with them). Grimoire Card The Coven
Oryx could kill her, if she holds on too long.” Sedia offered through the silence, fearing what was to come."
Sedia is one of the Techeun’s who helps her summon the Harbingers. Also from the same card:
"What if they are not wise enough for the Dreadnaught?”
Llyn turned back to the source.
“Sedia, do you not have faith in our queen.”
So here we can presume that Mara Sov is indeed alive. How she is faring, though, can only be guessed. With the power of the Harbingers, she obliterated the Wolves and their Kell on Ceres, and also managed to wrestle control of them. Maybe she could do the same with the Taken.
The Awoken are politically obligated to declare the death of their monarch if she isn’t found to be alive. That doesn’t mean they are the final authority on Mara’s status; they just have no reason to believe otherwise yet.