I don't think they would even consider splitting up completely. They are a family after all. I'm pretty sure that they are still in the New World, somewhere in Whitebeards ex-territory, trying to reclaim it from Blackbeard. I think Luffy will meet them at some point and assist them in getting their land back (but they will fail to defeat Blackbeard, as he is the "main villain" after all)
We can be sure that they did not try to have their revenge on Akainu. That would dishonor Whitebeards last orders. Besides that, it would be very stupid, too.
They are a family but one of pirates at that. WB was the leader of the family, the pillar that held it together. I don't think they would outright hate each other however it is indeed strange that a crew with those 14 commanders would be pushed around even by another yonko. More so, they are not even counted among the yonko anymore. Even with WB gone, that is incredibly strange if we consider the main crewmembers have remained together. The crew must have gone through hell in many levels. With WB dead, it is extremely likely that most of the territory they controlled was attacked in some form. Add in yonko trying to expand, strong new world crews seeing a chance to get influence, lowly pirates trying to make a name for themselves and finally good old BB rampaging with a crew with a bunch of people comparable to the commanders. Add in the grieving the crew must have gone through and who knows what else... I really don't see the WB being anything other but remnants of what they once were.
Seriously, even without WB a crew with those 14 commanders is a massive force, once that made the world government gather every asset they had in hand to fight them. Why would BB be able to take their position as a yonko that easily? Why would they be an unnamed force in the balance of power in the new world? Heck, we readers saw some superiority in terms of rank in the crew but I really do doubt his actual rank was any higher than that of the other commanders. Honestly, what the WB pirates lost in that war was huge.... I could easily see the strawhat pirates split up if luffy dies too (not relevant but it is a good comparison).
I think Marco didn't join other crew but is still leading WB pirates with some of the original crew but also with new faces that joined during those 2y . Well i'm still not sure if the others captains are still united ( most probably some have chosen to make their own crew and revenge WB and some have failed and died) but i think at least 1 or 2 captains remained in the original crew.
Marco was a guy who was completely loyal to WB , at least that's my view of him so i don't think he joined Shanks . He is strong enough to lead the WB pirates
I have said in the Discussion Thread that when a rookie Makes it to the New World, and sees the difference between him and the veteran pirates there, the captain may swallow his pride and join a strong pirates crew, now who's stronger than a Yonkou, and I gave the example of Rockstar who joined The Red Hair crew, that said, I think if not most of them then some of them joined Kaidou, Big Mom or Shanks. The only Yonkou I can see them not joining is the one "Behind" Their captain's death ... BLACKBEARD. IMHO
I think its highly unlikely to expect the WB pirates to join up or form another crew. As Marco said when Ace first joined they were all detested misfits that finally found a home under the name of Whitebeard. Being a family is what they took pride in, they all would have gladly died bearing the name of WB. There is just way too much love, pride, and respect among the WB pirates for them to ever abandon that name. WB sacrificed himself so that they could be apart of the new age. I don't see any of them suddenly saying "What the old man did was nice, but i'm going to go off and do my own thing". If you are willing to truly give up your life, as the WB pirates were, for a name and a symbol then you usually don't abandon that after the leader is gone. If anything your connection to that name and symbol only grows because now it has that much more significance to you.
And what exactly did the name and symbol of WB represented? Pirates are by definition selfish, they were not revolutionaries giving themselves to a cause which they believed greater than themselves. The WB pirates are no exception, even during the war they were not fighting for freedom, values or the greater good. They were fighting for their own. I would argue the WB pirates were bounded mainly by WB because they genuinely cared for WB however we have never had any reason to believe that the man himself ever stood for anything which he or his crew upheld to be greater than themselves or of objective value. The WB pirates were bounded by their limitless loyalty to WB who they saw as their father but the father is gone now. Isn't it normal for children to eventually take their own path? Who in that crew could ever possibly take the role of WB? Marco was obviously WB's number one however saying he is fit to take the mantle of WB of such a gargantualy powerful crew and such territories over so many pirate crews with reasonably powerful commanders is a bit much. Marco ultimately has neither the respect, the power or the presence of WB. I don't see him becoming the father of the crew and loyalty for him is far from the same as loyalty to WB.
They don't need a second Whitebeard to lead them, I believe all commanders consider themselves equal so IMO it wouldn't be strange if they reformed into some sort of a democratic pirate alliance(operate individually but under WBs flag, having council meetings). That way they wouldn't be considered a Yonkou even if together their territory would be bigger than Blackbeards, normal people who read newspapers would think that they're just remnants of WB desperately trying to protect their captains legacy.
I think much of the allied pirates went their own way. It's hard to believe each allied captain would stay in alliance now that Whitebeard is dead. He was the man they rallied around. The fact that Blackbeard stole much of WB territory proves that WB Pirates aren't as influential as they were. In fact, I wouldn't be surprised if some of the main crew joined Shanks, like it was foreshadowed with Marco.
Still, I think Marco is now captain of the WB Pirates and that they still hold some of their territory.
the Morale of the WB pirates had to be at an all time low and it's never a good idea to head into a battle in that kinda situation and since he knows the territory so well and has the Quake DF it should be easy to sink attacking ships and how would you deal with that it you were Marco.
BTW does anyone think that maybe Capt Kidd joined up with BB??