Do you believe God is omniscient right now?
If yes, that means He knows everything right now.
If He were to change tomorrow, that means He did not know everything right now.
If God is omniscient, there is no reason to change. God does not depend on us for anything. He does not change for anything we do or don’t do.
(Deut 28:63) "And it shall come to pass, that as the LORD rejoiced over you to do you good, and to multiply you; so the LORD will rejoice over you to destroy you, and to bring you to nought;..."
God rejoices no matter what you do or don't do.
God is fully omniscient, now and always. He always knows everything knowable. To not know a nothing is an absurdity.
God's omniscience is dynamic, not static. As new objects of possible knowledge become certain, the objects of God's knowledge change so His knowledge changes. He can experience novelty, new things, etc. because He is personal. He can delight when a new baby is born or a sinner becomes a Christian. He is not stuck in a boring eternal now simultaneity.
God is responsive. He does not need to change, but the nature of the future is objectively anticipatory and contingent. As the the potential future becomes the fixed past through the present, God knows reality as changing from possible to certain/actual. It is not that God changes so much as that the objects of knowledge are changing (if the future was fully settled/determinism, then God would know it as such; since the reality of the future is partially unsettled, God knows it as such). In all this, God is fully omniscient whether He knows things as actual (past/present) or merely possible/probable (future).
The past is inherently different than the future, so an omniscient being's knowledge will reflect this without compromising being all-knowing. If the future was settled, God would know it exhaustively. Since it is not, He distinguishes possible vs actual.
Determinism makes EDF possible, but determinism is false. Free will theism necessitates dynamic omniscience since EDF is incompatible with libertarian free will. Since God experiences endless time, not timelessness, it will have implications on the nature of omniscience, future, free will, predestination, etc.
God rejoices when appropriate. It also says He grieves, regrets, hurts, etc. when appropriate. God does not rejoice no matter what.