The gorosei very very rarely ever leave marijoa. This is most likely due to how detrimental it would be if one of the gorosei were to be captured. The thing that the world government values most, is their secrecy. This is because they know if their secrets were to be revealed that would lead to their downfall, and therefor would desperately do anything to prevent this from happening. The reason the gorosei are now willing to risk leaving marijoa is because the situation has become so desperate since vegapunk is studying the void century.
A gorosei leaving marijoa is extremely rare and there is not a chance he will simply return back to marijoa. Obviously Oda is going to make something out of this to advance the plot. The major incident is obviously going to be a gorosei being captured which will lead to more of the government's secrets being leaked. Oda has also said that he was going to reveal more and more about the void century secrets.
While Kizaru and the marines have their hands full fighting the strawhats, whatever person on the blackbeard ship will come and abduct saturn. Laffite is the perfect person to hypnotise saturn and make him spill everything. This will be the starting step for blackbeard to make his moves of becoming king of the world.
A gorosei leaving marijoa is extremely rare and there is not a chance he will simply return back to marijoa. Obviously Oda is going to make something out of this to advance the plot. The major incident is obviously going to be a gorosei being captured which will lead to more of the government's secrets being leaked. Oda has also said that he was going to reveal more and more about the void century secrets.
While Kizaru and the marines have their hands full fighting the strawhats, whatever person on the blackbeard ship will come and abduct saturn. Laffite is the perfect person to hypnotise saturn and make him spill everything. This will be the starting step for blackbeard to make his moves of becoming king of the world.