I agree that it's the least likely, although I still don't know why they would have intentionally exempted this from their previous decisions when they could have covered both in one go.The same argument was made by Trump then as now so I suspect the same outcome. They will deny the stay and it will revert back to the courts ruling. Or they may grant a stay and then deny cert which is probably the next most likely outcome according to some legal interweb folk. Or scotus may take arguments and decide to rule with the courts. Ruling Trump is immune is the least likely outcome though even without that ruling it may delay things past the election which would be bad.
The most likely scenario is to stay and delay until after the election. If Trump wins then they don't have to do anything.