Frame of reference is key when considering something subjective like soon. It doesn't matter if there's an infinite God to whom "soon" is a million years. It's the frame of reference of the people receiving the message that is important.
For humans soon can still be seconds, minutes or even years. It's still subjective. What it can't be though is more than the lifetime of a human. That's not soon in anybody's book.
You might say, wait a minute. The Yellowstone Caldera is going to explode soon and that might be thousands of years from now. Yes, but the frame of reference for that "soon" is in a geological time, not human lifespan time.
The message was for humans and the frame of reference was human, so although the term soon is subjective it cannot exceed a whole human lifetime.