The past, present, or future tenses of a report concern the content reported. If eternal divine speech concerns a future event, the event occurs in the future; that does not entail a transition in God from not knowing to knowing or from not speaking to speaking.
“The event will happen tomorrow” and, afterward, “it happened yesterday” can each be true relative to their respective times. Temporal wording relates to an event's time rather than the origination of the eternal divine attribute.
Thus a report's time-qualified content and the eternality of speech are distinct.