Jump right in! I’ve barely been around much longer, and no one has told me to be quiet yet!
That’s a interesting point. And, of course, there’s also the sense in which everything has always been under God’s rule, since He is God after all. The passage itself seems to have at least some of this in mind, and that’s kind of the point. “For ‘God has put all things in subjection under his feet.’ But when it says, ‘all things are put in subjection,’ it is plain that he is excepted who put all things in subjection under him. When all things are subjected to him, then the Son himself will also be subjected to him who put all things in subjection under him, that God may be all in all” (1 Cor 15:27-28).
The book of Hebrews also quotes Psalm 8, and then says this about it, “Now in putting everything in subjection to him, he left nothing outside his control. At present, we do not yet see everything in subjection to him” (Hebrews 2:8). So it seems the New Testament recognizes that although Psalm 8 says that all things are subject to Christ, yet there remains some things which are not yet.
It’s worth noting, also, that Psalm 8, at least in the ESV, seems to speak more about ruling over all: “what is man that you are mindful of him, and the son of man that you care for him? Yet you have made him a little lower than the heavenly beings and crowned him with glory and honor. You have given him dominion over the works of your hands; you have put all things under his feet, all sheep and oxen, and also the beasts of the field, the birds of the heavens, and the fish of the sea, whatever passes along the paths of the seas. O LORD, our Lord, how majestic is your name in all the earth!” (Psalm 8:4-9)
What to make of all this? I have no idea.