I can see how some things can be either of them ("Grandmaster" variation).
That said, the majority of those intro quotes seem to point at Bi-Han, IMO.
Sure, Kuai can come back if all the souls are set free, which can happen.
My point, though is that it doesn't HAVE to happen.
Shaun Himmerick alluded to the souls still being under Quan Chi's control, in the Quan Chi release trailer, which is what makes me doubt Kuai for MKX.
When you also factor in "30-something characters" in MKX (per Ed Boon), I don't see all of those dead characters being set free from Quan Chi and being playable in MKX (as it would have a roster close to 40 characters).
I could easily see NRS writing into the story something that leaves them the option to add those characters back to a future MK (Quan getting killed, at the very end), if the MKX new characters don't fare well with the fans.
MKX isn't the fan-letter game.
MKX is the testing the waters game, which is why I also think that Bi-Han being back, burying the hatchet with Scorpion (something that wasn't done in the old timeline) and testing the waters with a new MKX story is a possibility.