From Reddit:

Captain Lannery Storm: So now we have 4 Lotus Petal-ish varaints. Lotus Petal, Tezzeret's Etherium Cell tokens, Gold tokens in Theros, and Treasure tokens in Ixalan.
Sunpetal Grove: About time for a reprint. Presumably the whole cycle, or the allied half of it at least.
Sorcerous Spyglass: Pithing Needle+Peek (-cantrip). Seems fine.
Arcane Adaptation: Strictly better Conspiracy
Vanquisher's Banner: Probably will be popular in tribal EDH decks. I doubt it'll see a huge amount of play in other constructed formats, with that mana cost.
Daring Saboteur: Depending on it's full mana cost (probably 1U) and P/T, seems like a reasonable looter.
???ing Insight: 7-drop wheel, possibly.
Jace, ??? Castaway: His ult makes copies of himself. Depending on the rest of the card, potentially terrifying.

A comment from the Reddit thread:

It could be the only way to first get to Ixalan is to become "truly lost" in the multiverse.
Like the Pirates of the Caribbean quote:
"For sure, you have to be lost to find a place that can't be found, elseways everyone would know where it was. "
Maybe Jace is some kind of Aether Castaway.

That means we'll see Fblthp on Ixalan, right?

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Next Duel Decks after Goblins vs. Merfolk: Fblthp vs. Ragavan. Which piratical mascot will reign supreme?

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Squee.

So a second photo of the same sheet is casting doubt on whether this is real. In particular:

• A mono-green merfolk
• A mono-white vampire
• One card with Raid
• One Vehicle
• Jace, ____ Castaway seems to have a supertype
• A creature named "Hostage Taker" gives infinite ETB triggers all on its own, and causes a draw if there are no other creatures or artifacts in play.