They are created now. The revelation to man of what has lain secret in God's counsels from all eternity is a sort of creation. As Nagelbach well says, it converts the λόγος ἐνδιάθετος into a λόγος προφορικός and therefore is one step towards actual accomplishment.
The mystery of "the Servant of the Lord," and of atonement and salvation through him, had hitherto been hid away—"hid in God" (Ephesians 3:9), and was now for the first time to be made known to such as had "eyes to see" and "cars to hear" by the teaching of the evangelical prophet.
Even before the day when thou heardest them not; rather, and before to-day thou heardest them not. Whatever shadows of evangelic truth are discernible in the Law and in the earlier psalms, they did not constitute a revelation of the way of salvation at all comparable to that contained in Isaiah's later chapters.
Lest thou shouldest say, Behold, I knew them. If the "new things" of Isaiah's prophecy had been revealed many centuries before, they would not have impressed the Jews of Isaiah's time, or even of the Captivity period, as they did by having been reserved to a comparatively late date.
They would have seemed to most of them an old and trite story.