I spent some time doing research and think that I have found the relevant quote from Justin Martyr. It comes from Dialogue with Trypho Ch. 52. The passage is copied and pasted below. In this particular passage, it appears that Justin is not claiming that there were both prophets and rulers among the Jews until the present time. In fact, he appears to be sarcastically claiming that this is what Trypho believed. I see this in that Justin says “that in your nation” He is putting this statement into the mouth of Trypho. After this quote, Justin says, “For though you affirm…” So, your question implies that Jesus and Justin disagree on this, whereas it appears that it is Trypho who disagrees with Jesus.
Let me be honest, I am not absolutely sure about my interpretation of this dialogue, but it appears to be the most reasonable analysis of the dialogue. In any case, if I had to decide who to believe–The Jews and Jesus or Justin–I would believe Jesus. Justin is not an inspired writer and Justin made errors, but in this case, I do not believe that you are quoting Justin in context, so the question is a non-sequitur.
“And it was prophesied by Jacob the patriarch21122112
that there would be two advents of Christ, and that in the first He would suffer, and that after He came there would be neither prophet nor king in your nation (I proceeded), and that the nations who believed in the suffering Christ would look for His future appearance. And for this reason the Holy Spirit had uttered these truths in a parable, and obscurely: for,” I added, “it is said, ‘Judah, thy brethren have praised thee: thy hands [shall be] on the neck of thine enemies; the sons of thy father shall worship thee. Judah is a lion’s whelp; from the germ, my son, thou art sprung up. Reclining, he lay down like a lion, and like [a lion’s] whelp: who shall raise him up? A ruler shall not depart from Judah, or a leader from his thighs, until that which is laid up in store for him shall come; and he shall be the desire of nations, binding his foal to the vine, and the foal of his ass to the tendril of the vine. He shall wash his garments in wine, and his vesture in the blood of the grape. His eyes shall be bright with21132113
wine, and his teeth white like milk.’21142114
Moreover, that in your nation there never failed either prophet or ruler, from the time when they began until the time when this Jesus Christ appeared and suffered, you will not venture shamelessly to assert, nor can you prove it. For though you affirm that Herod, after21152115
whose [reign] He suffered, was an Ashkelonite, nevertheless you admit that there was a high priest in your nation; so that you then had one who presented offerings according to the law of Moses, and observed the other legal ceremonies; also [you had] prophets in succession until John, (even then, too, when your nation was carried captive to Babylon, when your land was ravaged by war, and the sacred vessels carried off); there never failed to be a prophet among you, who was lord, and leader, and ruler of your nation. For the Spirit which was in the prophets anointed your kings, and established them. But after the manifestation and death of our Jesus Christ in your nation, there was and is nowhere any prophet: nay, further, you ceased to exist under your own king, your land was laid waste, and forsaken like a lodge in a vineyard; and the statement of Scripture, in the mouth of Jacob, ‘And He shall be the desire of nations,’ meant symbolically His two advents, and that the nations would believe in Him; which facts you may now at length discern. For those out of all the nations who are pious and righteous through the faith of Christ, look for His future appearance.