Since the Qur'an repeatedly states that the Message has been completed, perfected, saved and protected for all times, there is no question of a messenger after the exalted Muhammad (S). [The Perfect Divine Guidance through the Prophet shall be preserved in the form of the Qur’an for all times and all people 6:34, 6:91, 6:116, 10:64, 15:9, 18:27, 41:53, 75:16-19.]
Suggestion: See how much better (S) looks compared to SAW or PBUH.
Let us look at other verses in QXPv. And the context of 3:81 is addressing the Israelites.
3:78 Among them is a group who distort the scripture, to make you think that what they relate is a part of the scripture, when it is not from the scripture. And they assert that it is from God, when it is not from God. Thus, they tell lies concerning God, and they are well aware of it. [2:101]
3:79 Never would a human being, whom God has blessed with the scripture, wisdom and prophetic office, thereafter say to people, “Be servants of me instead of God.” Rather, he would say, “Become true devotees of the Lord since you learn and teach the Book and study it as it should be studied.”
3:80 Nor would he instruct you to take angels and the Prophets for lords and patrons. What! Would he ever enjoin upon you unbelief after you have surrendered to God?
3:81 Remember! God took a solemn promise from all Prophets (and through them with their respective nations that they would welcome each of the next Messengers in the process of Divine revelations and support him.) God said to the Prophets, “Now! I give you the Book and wisdom. Afterward there shall come a Messenger confirming (the truth in) what you have. You must, then, acknowledge him and help him. Do you accept and agree to hold on to this pledge of Mine?” They said, “We do agree.” He said, “Then bear witness, and I am with you among the witnesses.” [This was the promise with their nations. The personal covenant made with each Messenger is mentioned in 33:7. See 2:101 & 3:78 for ‘the truth in’]
33:7 And remember, We did take a solemn pledge from all the Prophets, and from you (O Prophet), as well as from Noah, and Abraham, and Moses, and Jesus son of Mary. We took from them a very solemn pledge. [3:81]
33:8 That God may ask the truthful about their truthfulness. And He has readied an awful suffering for the deniers.
[In the Hereafter, the truthful shall stand as witnesses how the Prophets conveyed their messages and how their people received them. Also see 3:81. The Covenant: Each Prophet will clearly convey the revelation to his people, live by the revelation and try to establish the System. And that he would support the mission of the previous Prophets. 2:83, 3:81, 3:187, 5:7, 7:169-171, 42:13. Since there will be no Prophet after Muhammad (S), his people will be questioned how well they conveyed the Qur’an]
3:187 God accepted a solemn pledge from those who had received the scripture, “Make it clearly known to people, and never conceal it!” But they flung it behind their backs, and traded it away for a little gain. How evil was the bargain they made! [2:16]
5:7 Remember God's blessing (guidance) upon you and His Covenant binding upon you when you said, “We hear and we obey.” Be mindful of God. God is fully Aware of what is in the hearts. [1:4-5]