Here's what will happen.
A fake investigation will be concluded with some SA officials set up as the 'rogue killers'. These scapegoats will have an SA show trial and go to prison (quietly released weeks later, and kept in the lap of luxury while there).
Turkey will accept this. They will not release the tape. If it is somehow inadvertently released, they will call it fake. They will do this because KSA will give them many hundreds of millions of dollars in oil and cheap loans to do so.
The US administration will gleefully accept this narrative and all goes back to as it was before. The weapons sale goes through. The gas price doesn't rocket.
The rest of the West, bar some grumbling in some quarters, and a few harsh questions at the UN, will hold their noses and accept it as the price of doing business, and business is good.
The world limps on. The attention of the West swings onto the US mid-terms.
Jamal Kashoggi's partner lives with the awful knowledge that her man was horrifically tortured to death, and that the world took a bribe to look the other way.