Vegapunk’s message is just beginning, he’s going to explain more in next chapter(s).
Considering how badly the Gorosei and Imu want to hide this and the fact that the only other instance of sea level rise we saw this arc was a result of the weapon being fired, it’s pretty obvious
And, this is where my issue arise.
Throughout the story not once it was mentioned that sea level is rising.
Only time it was brought up was during Lulusia incident.
One thing is certain that WG wants to rule the way it is so VP can't reach to the conclusion that world will definitely sink based on one incident.
But you do have a point because we have direct evidence of WG use of weapon causing it.
However, if you read the panel then sea level rise happened because of an earthquake caused by use of weapon.
So, what if this is link with red line?
Because they are losing their control over the world.
No such indication as of now