The marines are joining them as well. My guess is there will be a huge battle, we'll only get to see or hear about the aftermath. I think the fact that they're battling is what's going to allow the Strawhat crew to get into the New Line, since the marines are going to be busy elsewhere. I also believe that Whitebeard will die in the battle, Asce will be saved by his sacrifice, and the Whitebeard Pirates will be splintered apart. On the other hand, I think the marines are going to be devastated, and at least one of the Shichibukai will die in the battle as well. Asce may actually meet up with the Strawhats again and join them again, especially if Whitebeard dies.
Aren't we talking about the strongest pirate? or strongest person?
It's still too early to speculate about this I think. We only know 2 out of 4 yonkai.
actually, we are talking about both. Whitebeard has the title of the world's strongest man already, even though we haven't seen any other yonkai. so, if blackbeard manages to kill him, then he would gain whitebeard's title as world's strongest man. also, since blackbeard is still a pirate (just one employed by the world government), he would in turn gain the title of world's strongest pirate. make sense?