The term translated as "given by inspiration of God" in the KJV of 2 Tim 3:16 is the Greek term θεοπνευστος (alt: "God-breathed" [NIV]). Some Protestant apologists argue that, as the Bible is said to be the only authority said to be θεοπνευστος, it is the final, formally sufficient authority, and Christians have no need for an authoritative Church or additional revelation, such as the Book of Mormon.
However, we can't help see that such apologists are guilty of a number of logical fallacies. Firstly, 2 Tim 3:16 is speaking of the nature of "Scripture" and that it is inspired by God. However, it is simply begging the question to claim that "Scripture" and "the Bible" are one-to-one equivalent with one another; the scope and extent of the canon is not in view in Paul's words to Timothy.
Furthermore, θεοπνευστος appears only once in the Greek New Testament; it is never used in the LXX. Now, if a Protestant wishes to argue that as the "Bible" is said to be θεοπνευστος, and such a term is not said to describe any other authority, what about the time prior to the inscripturation of 2 Timothy 3:16? If the apologist were consistent in their (admittedly, misapplication of) “logic,” no one could state with any assurance that Scripture was inspired of God prior to Paul using the term θεοπνευστος! Such is the absurdities of this "argument." In reality, for something to be inspired of God and an authority, there are different locutions one could use (e.g., "the Spirit of your Father which speaketh in you" [Matt 10:20]; "in spirit" [Matt 22:43]; "filled with the Holy Ghost" [Acts 4:8]).
Note the words of Paul in 1 Thess 2:13:
For this cause also thank we God without ceasing, because, when ye received the word of God which ye heard from us, ye received it not as the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe.
Here, Paul refers to both his inspired writings and oral teachings as being equally authoritative and as being "the word of God." As they say, "if it looks like a duck and quacks like a duck . . ."
As for comments from the Book of Mormon prophets recognising the inspired nature of their writings, see the following examples: 1 Nephi 6:1-6; 9:2-6; 14:25, 28; 19:2-3; 2 Nephi 5:30-31; Words of Mormon 1:3-9; Alma 37:1-25; 3 Nephi 26:6-12; 28:24-25; 30:1-2; Mormon 5:9; 8:13-16; Ether 4:1-6; 5:1-6; 8:26; 13:13; 15:33; Moroni 9:24; 10:2-5.
Protestant apologists who use this argument are guilty of eisegesis, begging the question, and special pleading, a lethal mix of abuse of Scripture and logic, though such is common in efforts to prop up a man-made doctrine like sola scriptura.