Isaiah 44:6 (KJV)
6 Thus saith the Lord the King of Israel, and his redeemer the Lord of hosts; I am the first, and I am the last; and beside me there is no God."
It is interesting that you would pick Isaiah 44:6 as a Scripture. IT actually emphasizes the "Oneness" of God by stating that
"Beside me there is no God".
When we dig deeper into that phrase we see that the personal name YAHWEH is used of both the King and His Redeemer, the one referring to God the Father and the other referring to God the Son. God's sovereignty is then emphasized by the fact that He alone is able to predict the future.
God asks the question "Is there a God beside me, yea there is no God, I know not of any".
The ONENESS which is the Trinity ask a question and then answers His own question. "I KNOW NOT OF ANY".
What is saying clearly is that He, the Trinity is the ultimate authority on divinity and to prove it, He accuses the other "gods" of being nothing more than idols made by men.
Now for prophesy, those who are determined to deny the possibility of supernatural prediction of specific events seem determined to interpret such things right out of the Bible even contradiction the interpretation of the same events by New Test writers.
We at times tend to forget the totality of Scriptures because we see in Matt. 3:17......
King James Bible
"And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased."
Then in Matthew 17:5..... (KJV)
5 "While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased;
hear ye him."