It seems to me that the lynch pin to this issue is the use & understanding of the word "prophet" in the 1st Cent. & before, as it had a more faceted meaning than that of latter times in 'Christian' circles. On top of that, during our 20th/21st century it is primarily applied to a person who foretells the future exclusively, whereas in the 1st century and before this was not the case.
We have to try and understand the scriptures with the eyes and mind of persons that live at that time according to the culture & customs etc. of their day not ours. It would seem that the word "prophet"* had/has the emphasis on forthtelling* not on foretelling or to quote from the 'Lexicon to the Old and New Testaments' Ed. by Spiros Zodhiates, TH.D in 'The Hebrew-Greek Study Bible', AMG Pub. page 172:-
"A prophet prophesies, but one who prophesies is not necessarily a prophet"**.
*or "forth" and "to speak" or "one who speaks forth openly."-'Vine's Expos. Dic. of Bi. Words' pp. 492-3
*Note: The Hebrew word translated by the into the word "prophet" is "nabi" which has the same basic meaning as the Greek "prophet" which is "one who speaks for another, or "his mouth." (Vine's Expos. Dic. of Bi. Words' pp. 190) which obviously includes telling of future events but not exclusively that, e.g. Ex. 4:16, 7:1. Also see the foot note no Ex. 7:1 in the N.I.V. study Bible.
**N.W.T. Titus 1:12 "A certain one of them, their own prophet*, said: “Cre'tans are always liars, injurious wild beasts, unemployed gluttons.”"
*Epimenides, a Cretan POET of the sixth cent. B.C.E.
I think it makes the point that how we today see the usage and meaning of ancient words is not how they where used or understood in or about the 1st century or before that time. My research shows me that "prophet" (and related words) have a much more extensive meaning than that which is common to us today. A prophet would seem to be a person of wisdom, an interpreter for the inspired oracle, a preacher of God's word or will (e.g. spokesman), a poet, and lastly a foreteller of events. Thus Abraham was a "Prophet" in that he did all of the above a a patriarchal Head of a Godly family and a forefather God's old nation of Israel which would lead to The Messiah and the Christian congregation speaking of God's promise to him and his offspring:-
NWT Romans 4:16, 17 "That is why it is through faith, so that it might be according to undeserved kindness, in order for the promise to be sure to all his offspring, not only to those who adhere to the Law but also to those who adhere to the faith of Abraham, who is the father of us all. 17 (This is just as it is written: “I have appointed you a father of many nations.”) . . ."