From this verse, we can infer that the Gospel, God's good news, is a promise or a set of promises made to man (for prophets were God's spokespersons to the people). Thus, certain promises referred to in various parts of the Bible: Acts 26:6,7; Rom.9:4; 2 Cor. 1:20; Gal. 3:16; Eph. 2:12; Heb. 6:12; 10:23 are actually referring to the Gospel, God's good news to us.
Now, if the Gospel or good news is a promise or set of promises to us, it means that these promises are good things!
Additionally, if God made these promises a long time ago (the prophets referred to in this verse wrote thousands of years ago before Paul and the birth of Jesus) about His Son who had already died and resurrected (see verses 3 and 4), and Paul was being sent to deliver the good news, it means that at least, some of these promises had been fulfilled and the fulfillment of the rest were already in motion.
This fulfilment of God's promises thousands of years after they had been made is unequivocal proof that our God is a faithful God! He doesn't forget His word/promises and He keeps them. He made a promise thousands of years ago about what would be accomplished in and through His Son in the far distant future and when the time came for the fulfillment of His promises, God fulfilled them.
This means that it does not matter how long it tarries, God does not forget His word nor has He forgotten it and that thing which He has spoken, He will surely fulfill and bring it to pass.
Therefore He saith, “For the vision is yet for an appointed time, but at the end it shall speak, and not lie: though it tarry, wait for it; because it will surely come, it will not tarry.” Hab. 2:3
Num. 23:19: God is not a man, that he should lie; neither the son of man, that he should repent: hath he said, and shall he not do it? or hath he spoken, and shall he not make it good?
See, time isn’t a hindrance to God. He exists outside of time and is never late for Scriptures teach us that He hath made every thing beautiful in his time (Eccl. 3:11a) and that He is the God who quickeneth (makes alive) the dead (Rom. 4:17). The birth of Isaac and the resurrection of Lazarus are poignant examples in this regard.
Other Scriptures on the assurance that God's promises to us will all be fulfilled include,
Then said the Lord to me, You have seen well, for I am alert and active, watching over My word to perform it.
And Isaiah 55:11 (AMP):
So shall My word be that goes forth out of My mouth: it shall not return to Me void [without producing any effect, useless], but it shall accomplish that which I please and purpose, and it shall prosper in the thing for which I sent it.
These Scriptures and many more show us that God is faithful and His promises to us are sure!
Therefore as the writer of Hebrews admonishes,
Cast not away therefore your confidence, which hath great recompence of reward. For ye have need of patience, that, after ye have done the will of God, ye might receive the promise. Heb. 10:35,36.
Another thing we can learn from Rom. 1:2 is that, ours is a God who speaks. What He was going to do, He spoke of thousands of years ago. He still speaks today of things to come: John 16:13. Hallelujah! We can see the future!