Well, now it's getting to Raftel. That was always the ultimate goal and that's their main goal right now.
But this time it is different. Before it was just a simple point on a map and regular location for the people of the world. Raftel by comparison has to be competently hidden and/or very hard to reach place for some reason. Otherwise every one of the Emperor could have get the One Piece long ago. Oda has still to explain, why nobody of them just casually traveled their and if you need to become a Emperor, besides them naturally be in your way.
The clues up to this point make it look like, you need to read all of the Poneglyphs to find its location. This would explain, why the other Emperor just couldn't casually went their and your have to enter enemy territory to get access to all of the Poneglyphs. Since their was a very balanced power level between the forces up to this point, the battle for the crown was a stalemate. It could also be, that only a few actually know the secrets about the Poneglyphs. Blackbeard still wasn't shown to know something about them, so their could also be an alternative way to Raftel.
All in all it would be great from Oda to finally explain us, what the overall goal and rules for this half of the story are.
He clearly stated that he wants to defeat all four emperors. And when Law proposed they team up to defeat Kaido, he told him "as long as Shanks is not the first". So.....
Ok, competly forget about that. But again, what is the point of this. Up to this point One Piece wasn't about "Fighting all the bosses" as an end-goal, there were just obstacles. I'm just wanna hear the why (But it could also be simply a "because Luffy wants to"-situation)