Chap 670 spoiler

670: Blizzard With a Chance of Slime
Cover: Franky arm-wrestles a gorilla while Robin interferes

Tashigi notices Luffy and attacks in smoke form, but is caught by him easily. He says "You've gotten weak, Smokey!"
Smoker attacks with his jutte and Luffy surprisedly remarks that "Glasses girl has gotten strong!" Robin realizes that it's because of Law's power and says so.
Luffy says, "You're... Smokey?" and bursts out laughing.
Luffy: "Let's fight for real next time. There's no point in going at it now if you're not at full power."

Franky brings down the gate with his laser.
A slime falls from the sky on the ship that Marines are trying to escape in and releases toxic gas. It attacks the Marines.
If they touch it, they're poisoned. When they burn it, it explodes and destroys the whole ship. A bunch of underlings are killed (taken down, whatever).
Slimes also fall onto Luffy's group. At the same time, Caesar appears.
He tells Luffy and Smoker to wait just a bit longer. He says that because the slime hates water, it's slowly shooting bits of itself across the lake."

Zoro and co. nonchalantly stare at the slime from across the lake.
Caesar: "From the blazing to the frozen lands! When the entirety of the slime arrives here... you'll all be consumed!! Four years ago, the-"
Luffy: "Gotcha!"
Caesar: "Ehhhhh!!"