I have read persuasive arguments both ways. To date I have not been able to determine what the material difference would be were it proven definitely one way or the other. I suppose I lean toward fourfold, since shepherding and teaching seem to be so intertwined. Yet, I have known men who were effective teachers but had no great gift for shepherding.
I have heard the five senses applied, as well as the fingers and thumb on a hand, and the four spices plus the oil of the holy anointing oil. I suppose each analogy has its merits. The most important thing, however, is that we better understand what these gifts look like in operation. How do we recognize an apostolic gift, a prophetic gift, etc.? The church needs these gifts in operation, now as much as ever. I provided brief descriptions of each gift in my book The Glorious Church (pgs.43-44).