So that's the end of the message ig??
The entire message is mostly dedicated to the one piece world to start moving their ass out and go search for those pieces........ basically Roger last words in a bigger scale..
Except the ancient city being buried underwater, actually nothing sort of huge secrets reveal and lore that benefits the readers from this message.
Remember when we're hype by the incoming message, with all the Gorosei having reaction that they'll get cooked if they let him say any single word. Now it's finished with successful say what all he's supposed to.
Have a feeling we we're just in a loop of void that nothing really happens during all that message.
Honestly this can be break down in 7 chapters or so.