We probably get Gamora back, just not exactly the one we had since the first GOTG. This Gamora is the one who travelled with Thanos and Nebula from 2014.
The way I see it, Quill was trying to locate her in that scene, possibly to set a course for her, and this might be what GOTG vol. 3 is about; although it's unclear whether Saldana's contract has her in it: a couple years ago, the whole cast was planned to be doing three volumes at least, but that might change.
As for Natasha, Hulk tells Captain America that he tried to bring her back along the rest but didn't manage to do it. If the Stones can't do it, then yes, Black Widow and "2018" Gamora are unlikely to come back for now. This is confirmed by a recent interview of the directors:
Q: Can you get the soul your sacrificed for the Soul Stone back when you return it?
A: No, the process is irreversible. Even if you have returned it to its original location, you wouldn’t be able to get the person back. In fact, it’s not really returning the Stone, more like put it back properly. The tribute soul for the Soul Stone will forever be sealed in that place, therefore Black Widow is gone forever.
'Avengers: Endgame’ directors just explained some of the movie’s biggest mysteries, BGR, April 30th, 2019
Sure, that's beginning with the case of the Soul Stone being returned (not other Infinity Stone shenanigans), but then goes on to "no, never, once you're dead it's over". If that applies to Black Widow, that applies to 2018 Gamora as well.