It's a yes or no type. Is belief in the doctrine of the Trinity an essential belief for salvation? Yes, or no?
Read Romans 10:9-10.
So, if it is possible that David and Moses and Abraham and Issac and Jacob were all saved without once mentioning anywhere in their writings or their traditions that God was three-in-one, then I would venture to guess that belief in the "Trinity" is obviously not an essential belief for salvation.
Now if belief in the "Trinity" is an essential element of salvation, then I dare say that none of the old testament people were saved.