By the time GTA6 comes out, which might not be til 2026, Xbox Series may be so dead in the water that not even GTA can help much, similar to how not even Mario Kart 8 or Smash Bros 4 could sell the Wii U.
Once a console gains a bad reputation, especially the infamous "no gamez" label, it's extremely difficult to turn it around. A few have managed to do so, like 3DS and PS3, but that was only through a herculean effort. For most, once the rot sets in it can't be undone.