Everything Oda's been doing in the New World is to set up Blackbeard's rise to power. We had Luffy get his Yonkou moment with Kaido, Buggy get his Yonkou moment by becoming one, and Shanks get his Yonkou moment by messing with Green Bull. So, Blackbeard is next, right? Caribou wanted to tell someone about Shirahoshi(Poseidon) and Pluton in Wano. Hmmmmmmmmm. We know Blackbeard loves history and wants power.
Outside of Wano is Zou and Whole Cake. If Blackbeard moves on Wano now, he can get the Road Ponyglyphs from Zou, Whole Cake, and Wano, as well as get Pluton, and Sukiyaki, a Ponyglyph translator.
Blackbeard spent all of the pre-time-skip biding his time until he could unleash total chaos at the end when everything was set up for him at Marineford. Same thing here. Blackbeard will attack Whole Cake, Zou, and Wano (I think he'll make Ace and Whitebeard zombies on Sphinx, too).
Oda has made it so that there is one Yonkou, Blackbeard, who has no Road Ponyglyphs. Oda has also made it so that three Road Ponyglyphs, a translator, and Pluton, are all in the same area. It's ZEHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA TIME!