I looked on IMDB to find out who played the Four Who Speak as One when I noticed that each one is given a name. Isa, Jer, Nahum and Mal. While one is immediately evident as a Biblical prophet (Nahum) the other three are commonly used abbreviations for other prophetic books (Isaiah, Jeremiah, and Malachi). While each of these prohpets were historically male, I have no doubt that the names of the Four Who Speak as One are intended to reflect the four Old Testament prophets and not just a coincidence. The question then becomes, does that mean anything in the shows story, is it setting up a possible plot point if they desire to use it later, or is it simply an Easter Egg for people like myself who stumble across the names and know their Biblical trivia?
Probably an easter egg/reference to their ability to see the future. They might have another appearance if and when Ichabod releases Katrina from Purgatory but other than that, they really don't add to the plot. Though I will admit I am impressed that you noticed the name allusions. Even I as a Christian did not see that so props to you. =)