I doubt Momonosuke is actually fighting Kaido. Luffy (Gear 4th) and Yamato vs Kaido yay.
Yamato has been very impressive. I was expecting the Thunder Bagua clash to result in the end of her fight, but she's still going strong. I didn't expect to go into this arc and have a Mini-Kaido team up with Luffy. With Yamato, and the quick development on Luffy's Haki, I think we can all agree he can take on everything Kaido has currently shown once he enters Gear 4th again. Only problem to wait on is Kaido's Awakening (I will riot if Doflamingo has Awakening, but SOMEHOW Kaido does not).
If Marineford 2.0 happens, Luffy has plenty of allies that could show up and really make a difference. Imagine Yamato rolling into Marineford with her own Newly-found Beast Pirates and clashing with Sakazuki personally in an attempt to avenge Ace. I genuinely think she has the power to win if she can avoid taking a direct hit from Sakazuki's magma.
The Straw-Hats, Grand Fleet (5,600), Wano Samurai (~5,000+), Minks (At least Hundreds, unless it is a smaller crew led by Carrot), New-Beast Pirates led by Yamato (Thousands including hundreds of Gifters), Possibly the Remnants of the WB Pirates, and potentially Elbaf warriors (if Elbaf happens BEFORE Marineford 2.0)... Luffy would have more people on his side than Whitebeard did when he went to save Ace.
- And we also gotta consider potential 3rd parties to show up... Revolutionary Army to align with Luffy... Former Shichibukai for different reasons (Crocodile wanting to fight Luffy, just like with Whitebeard)... Blackbeard himself... Hell, Shanks might even come here once again and this time, Luffy will get to properly meet him.
- Funny thought, all 4 Yonko would show up if you include Buggy, after he somehow takes credit for something big (imagine him landing on Elbaf after escaping the Navy, only to be caught up in Luffy vs Big Mom shenanigans), and Luffy since he'd have defeated Kaido by this point.
- And unlike Whitebeard, who stayed back to survey the battle-field, we ALL know Luffy would be the Spear-head for the vanguard. I think people like Nami and Usopp would stay back on the Sunny and fulfill the role of the strategists.
I know I got way off topic from the chapter itself, but frankly, I think Luffy will succeed in saving Sabo, otherwise nothing would have changed from Pre-TS, at all.