WARNING: The following contains spoilers for One Piece Chapter #1028, "Brachiosnakeus," by Eiichiro Oda, Stephen Paul, and Vanessa Satone, available in English from Viz Media.
In the most recent chapter of One Piece, it was revealed that defeating Kaido as well as stopping Onigashima from falling weren't the only problems the Straw Hats have to deal with. Currently en route is a fleet of World Government ships ready to seize control of Wano in case Kaido is defeated -- a fact completely unknown to anyone on Onigashima or Wano aside from the handful of CP-0 agents already there.
While this might seem like a huge problem, it's actually the perfect solution to the Onigashima bomb situation. As of right now, Momonosuke in his dragon form is trying his best to keep the island afloat in the sky while Luffy fights Kaido, with limited results so far. Kaido's aim was to use Onigashima as a way to wipe out any traces of the old Wano by dropping it directly onto the capital city.
To add to an already huge dilemma, the island is guaranteed to fall. If Luffy beats Kaido, the clouds holding the island up will disappear, dropping the island. If Luffy loses, Kaido will simply remove the clouds on purpose, which will also cause the island to drop onto the capital. The impact of the island itself would be enough to wipe out the capital, but with all the arms and ordnance on Onigashima, according to Yamato, the explosion could wipe out the entire country.
Currently, the island falling is the biggest concern for the Straw Hats because there's no option where it doesn't fall. Instead, their only real option is that Momonosuke manages to catch it in time and keep it afloat himself. However, if Momonosuke does manage to stop its sudden fall, he'll still need to have somewhere to put it. Thankfully for everyone on Wano, the World Government has decided to nose its way in.
With a fleet large enough for them to feel like they could take over Wano, the World Government isn't pulling any punches. While it's unclear whether it has the same destructive potential as a Buster Call, it's obvious that they're taking the situation very seriously. That being said, they have practically sailed their way into their own graves.
As Momonosuke is quickly learning how to use his powers, it's entirely within the realm of possibility that he will master control over his clouds. Once/if he does, he can move the island to wherever he chooses, just as Kaido can. If he were to see the ships coming, he could easily have the island fall onto the fleet -- and with all the explosives and weapons on it, the island's fall could potentially wipe out the majority, if not the entire fleet, in one fell swoop.
While this might seem like only a temporary solution, it would actually be more than enough. The Navy is already supposedly short-staffed and stretched thin trying to capture the recently criminalized Seven Warlords of the Sea. This is probably why the World Government is sending its own fleet instead of Navy ships. If this is indeed true, there probably isn't a backup fleet standing by or maybe even available to send in at all. Moreover, if the fleet that's being sent in has all their best soldiers, it would be pointless to send in a backup fleet in case the main one fails.
Unknowingly, the World Government has damned themselves in their misguided attempt at conquest. By hoping to take advantage of the situation, they have let themselves become vulnerable to the very same thing. Let's also not forget that Oda, the series creator, has been teasing a huge war to come at some point after the ending of Wano, so it's very possible that this is the catalyst that sets it all in motion.
With the Straw Hats on their way to beating the World's Strongest Creature, there's no way Luffy and his crew would let themselves lose to a mere fleet of ships. The only thing relating to the World Government that the Straw Hats need to be concerned about are the CP-0 agents currently on Onigashima. With their presence having gone completely unnoticed during the raid and a new mission to catch Nico Robin regardless of who wins, they represent the biggest threat to the crew's victory. That being said, the Straw Hats have proven throughout the series, and especially on Wano, that they won't let their friends down and won't be beaten no matter what.
