I guess Hawkins predicions takes a very low chance for Whitebeard. Whitebeard attack is more an suicide attack to save Ace. And it's no surprise, the Yonkou personality are even crazier than Luffy's when he tried to confront Crocodile or rampage Ennies Lobby.
If we measure the three great powers equality Whitebeard should already be lost. Although the Yonkou are not united. Thinking about it, it's possible that if the Yonkou united would be 2x the other sides, and that would make Whitebeard pirates = Marines or Shichibukai. And that's very scary, no matter it's "the great era of piracy".
That also make me think that those ugly folks from Shanks crew at chapter 1 (Lucky Roo, Yassop, who else) are really strong, like Whitebeard pirates?
The major problem for Whitebeard pirates are the 20+ Pacifistas. I can imagine Whitebeard fighting equally against two or three Pacifistas, but more than that would be his end.
And I don't think the Supernovas would join the battle. They are pirates for themselves, they have no reason for risk their lifes, with the chances against them, for another pirate. Whitebeard is an idol, Bonney cried because "her rock star was involved with drugs", bug I don't think she ever meet Whitebeard in person. Would Luffy join the battle if it wasn't for Ace?
Whatelse, even if 90% of Whitebeard pirates die, it would be a victory if they save Ace.