We're finally told that the prophecy came upon Nebuchadnezzar 12 months afterwards when one day he was walking on the roof of his palace and said "Is not this magnificent Babylon, which I have built by my mighty power and for my own honour and glory?" While he was still speaking God's voice spoke from Heaven, "O King Nebuchadnezzar, it is declared: You shall be driven away from your kingdom and from human society and you shall dwell with the animals of the field. You shall live like an animal eating grass like the oxen, and seven years (times) shall pass until you realize that the Most High God has supreme authority over the kingdom of mortals and gives it to whosoever He desires."
And so for the next seven years Nebuchadnezzar lived among the animals eating grass, and being rained upon while his hair grew as long as eagle's feathers and his nails grew as long as bird's claws.
At the end of that time period Nebuchadnezzar returned to his own mind and his kingdom was restored to him. The king was a humbled man ever after that and officially made proclamation that he praised, worshipped and honoured no other God but the King of Heaven. He had found out the hard way that He was able to bring low all those who walk in pride, but it was a lesson learned to the good of him spiritually. I believe that Nebuchadnezzar became a genuine follower of the God of the Jewish people. God loves all people and He will do whatever it takes to lead them into His loving arms. Nebuchadnezzar could have even rebelled against this discipline. But he did not. I fully expect to meet him in Heaven one day.