In a very good study of the term γραφη, Protestant scholar, L. Timothy Swinson wrote the following conclusion in his chapter the use of the term in 2 Tim 3:16 which refutes the claim Paul was teaching Timothy that "Scripture" is formally sufficient:
2 Timothy and γραφη
Over the course of three consecutive literary units (3:10-13, 3;14-17, and 4:1-4), as with the rest of the letter leading into these units, the main topic of Paul’s reflection and instruction is the apostolic gospel proclamation that Timothy has been commanded to guard, proclaim, and hand down to other trustworthy men, and for which he is to suffer persecution. Even with Paul’s brief reference to το ιερα γραμματα, he remains undeterred in his promotion of the primary subject of concern. Indeed, his remark concerning το ιερα γραμματα itself serves as one of the bases supporting the excellence of οις εμαθες και επιστωθης (3:14), or the apostolic gospel message. In view of the various criteria examined here, it seems highly unlikely that Paul would privilege το ιερα γραμματα alone as adequate to prepare Timothy for the duties that fall to him as the pastor in Ephesus and as worthy of his confidence. Therefore, on the basis of the close exegetical analysis of 3:14-17 in isolation, and as it fits within the more extended discourse of 3:10-4:4, πασα γραφη in its immediate literary context should be construed as a reference to the combined witness of the apostolic gospel message alongside all of the recognized OT writings.[37]
One final point must be acknowledged here. While the case has been made that πασα γραφη serves as a reference to the integration of the apostolic gospel teaching with the OT writings, unlike η γραφη in 1 Tim 5:18, it has not yet been shown that πασα γραφη in 2 Tim 3:16 must refer to a written form of that apostolic message. Certainly, a written form of the gospel message would suit the thesis of this study, as well as the exegetical criteria adduced in 2 Timothy. Indeed, the current prevailing position concerning πασα γραφη inherently presumes a written referent. However, based strictly upon the literary context of 2 Timothy alone, one need not conclude that γραφη or any of the other terms. Paul uses to refer to his apostolic teaching refers to a written gospel.
Note for the Above
[37] In truth, while the argument presented here is distinct, the position of the present study concerning this particular point does not differ markedly from that of Knight, who writes, “In this letter Paul has praised Timothy for following his teaching (v. 10), has urged Timothy to continue in what he has learned from Paul (v. 14) has commanded Timothy to retain ‘the standard of sound word’ that he has heard from Paul (1;13), has commended him to entrust what he has heard from Paul to faithful men so that they could teach others (2:2), and has insisted that Timothy handle accurately ‘the word of truth’ (2:15). After his remarks on πασα γραφη he will urge Timothy to ‘preach the word’ (4:2), i.e., to proclaim the apostolic message, about which Paul has said so much in this letter. It seems possible therefore, that Paul by his use of πασα γραφη is expanding the earlier reference to the OT to include those accounts of the gospel may have been extant and perhaps also his own and other apostolic writings that have been ‘taught by the Spirit’ (1 Cor 2:13; cf. for this view, e.g., Stott). This understanding also fits well in this context. It provides a reason for Paul’s use of πασα and for his change from ιερα γραμματα, an OT designation, to πασα γραφη, a possibly more inclusive term. It would gather together Paul’s concern for the preservation and communication of the gospel and the apostolic understanding and application of that gospel and place it on a par with the OT, as 2 Pet 3:16-17 clearly does. And it would provide a clearer background for and transition to his demand that Timothy ‘preach the word’ (4:2)” (Knight, Pastoral Epistles, 448)
Timothy Swinson, What is Scripture? Paul’s Use of Graphe in the Letters to Timothy (Eugene, Oreg.: Wipf & Stock, 2014), 158-59