There have been a few collabs over the years, some better than most (still love the Pirates Life one), though it's got me thinking, what other collabs are possible? I mean, they did one for Pirates of the Caribbean, one for Monkey Island, what's next?

Pirate 101

It's an old mmo rpg thats STILL kicking after all this time, though players have dwindled its still rather popular in Niesh communities!
It seems like an odd choice, yeah? Why Pirate 101? because of its near-limitless possibilities for stories and new content.
just think of the enemies you could add, from walking sharks, to undead zombies, to (what would make the most sense as the main antagonist) the clockwork armada.
and due to the countless number of iconic items from Pirate 101, you could have enough cosmetic items to fill TEN galleons!
While I'm no writer, i can see the tall tale now
A new enemy finds its way to the sea of thieves, one that runs on gears and steam, one who is hell-bent on finding a way to rid the seas of pirates forever, by locating the {insert deadly artifact here}, which could be used to destroy anything with ease.

Why would this work?
weeeeell it probably wouldn't, I mean, both games are falling in numbers, the only reason they would ever do something like this would be to get new players in both games.
Would THAT work?
Yes, 100% that would work, heck, if they do it right it could get thousands of players into both games.

another dumb suggestion from Captain Killer C Talent
sea-ya next time!