IMO The manga is about halfway done. They are halfway across Grand Line, so it would only make sense. bowser king is right, there are too many loose ends for it to end now.
I don't know who will win the battle. However, my greatest concern is still what will happen to Luffy and Ace. Of course, the battle between the Whitebeard pirates and the world government is very interesting, and they ARE the powerhouses of the world, but just because they rule the world does not mean they dictate everything that happens in the world.
'Justice' and 'freedom' are big issues in One Piece. The current world government operates using 'absolute justice' meaning any pirate can be taken prisoner or executed at any time for whatever reason. We also know that Luffy's biggest driving motive for becoming Pirate King is not power, but freedom. Luffy knows that the Pirate King has the most freedom out of anyone in the world, and he wants to be that man. Whitebeard offers his 'sons' freedom. He tells his sons something like, "If you follow me, you can GO WILD any way you want!" Because he is a the strongest force to fight against the marines, joining his group would give you freedom over the government's absolute justice.
Whoever wins the battle will only determine how different the conflict would be when Luffy enters the new world. I know I might be focusing a little too much on the protagonists, but ultimately, everything that happens in One Piece is meant to shape Luffy's journey.
If the marines win, Pirates will have a harder and harder time finding one piece. It would be the end of Whitebeard's era, the same as it was before when they ended Gol D. Roger's era.
If Whitebeard wins, the pirates would once again have rule. The main conflicts would be between the ruling pirates in the new world. We would find out a lot more about the current loose ends... Doflamingo, Vegapunk, Dragon, the other two Yonkou. Would the government be out of the picture? Not likely. Luffy would be definitely overshadowed by prestige and reputation... but as we've seen before, he can definitely defy all odds with his personality and fighting skill.
Either way, the story would be interesting, so I prefer to sit back and enjoy the show. I still even have questions about this current arc, so I can't really even try to predict what would happen after. I wonder if Sengoku has any powers? Will Luffy make it? (What's Boa gonna do when she sees him? Haha.) Will Blackbeard appear? What will become of Whitebeard, the admirals, and the shichibukai? These questions all have yet to be answered. And...
Will Ace die?
Bowser King
