Vegapunk might indeed Reveal some Void Century stuff
But We need to remember that He is considered Traitor & Evil Rebel
And Most World don't know much about History except their Own (To some Extent)
So Vegapunk Dying & then saying that WG are Evil & Accuse them of Crimes or saying that They aren't the Rightful Rulers ... etc
Isn't really gonna Shake The World, because from their Perspective, it's just an Evil Traitor trying to ruin WG's Image
Marines aren't gonna turn against WG because of what Vegapunk says, so let alone Kingdoms & Civilians
The Best that could happen is few Rebels like what happened after Sabo Incident
Vegapunk is instead known as Smartest Man & Best Scientist, People don't know him Personally, They don't think He is an Honest Person
But when it comes to Science? There is no else you can Trust more than Vega
So imo, Vegapunk's Announcement needs to be related to Science
Imagine Best Scientist's Last Words being about History & not Science, it would be Super Disappointing
Not to mention that Vegapunk have his own Personal Dream, He needs to entrust it to others in his Last Message
Poneglyphs were just a Recent Study for Vegapunk, it's his Science & Dream that instead defines his Life
This is why i believe Vegapunk's Last Words are gonna be about his "Greatest Scientific Discovery ever"
And throughout this entire Arc, Oda keeps repeating the Idea that some things are simply "Unscientific"!
It was literally Lilith's First Words, hinting that something that lies beyond her Understanding of Science
It was done again with Kuma, and again with Sanji, and Vegapunk mentioned it again against Saturn & much more
Even when Luffy & Co. met Atlas, She said the Question of "What's Real & What's not" have always been a Debate since ever
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In other words, there is No One in The World who studied more than Vegapunk, meaning if there is "Something" that even Science can't get you, there is No One better than Vegapunk to announce it, something that lies beyond Peak Science
Vegapunk must show Everyone Proof that this World isn't Fully Scientific & that there is a Treasure that completely defies Logic & have Miraculous Effects, while revealing that you don't need to Study to be able to get it
What is it? Vegapunk was Introduced with Ancient Robot that was Fueled by "Unknown Source"
I believe Vegapunk gonna announce this Energy Source & what it's capable of doing, saying that it's capable of Breaking any Scientific Limitations, which also happens to be his Dream (So He is basically passing it on to Everyone)
And how are WG gonna be Effected by this? It's Simple, He will Announce that this Powerful Treasure is Hidden in Mary Geoise & CDs don't wanna Share it, while also talking a little about Void Century with Giant Robot being Visual Proof of everything He is talking about
(Doffy did say that Mary Geoise National Treasure gonna Shake The World, and Vegapunk is Best Person to Announce it)
And just like Roger's Death increased Number of Pirates, i believe Vegapunk's Death will make so many join Revos Army, which is like Vegapunk's Gift to Dragon & also his Contribution to Revos Army