It's solid.
The only suggestions I had, I believe I left for you in the critique I sent.
If not, I certainly meant to, so I'll leave it here too.
Consider the source of said prophecy.
Who said it?
Where is it recorded (if it is)?
How is it recorder (if it is)?
How do the present-day people know it?
For it to be a prophecy, it has to have originated somewhere, through someone, and would have been written (or told) through their own perspective, and tell of events yet to come (which it does quite well, by the way).
It doesn't have to be accurate, or literal.
It does need to have a certain mythic feel to it (which you nailed, on both counts).
So rather than just leaving off on ~The Stone Kingdom; maybe point to the source more specifically.
~Engraving on the gates of The Stone Kingdom
- or -
~From the journals of the Prophet, (Bob, or whatever you want to call him or her).