Yes, it within the realm of plausibility that it could happen. But just because it's a plausible scenario does not mean its an even remotely probable scenario. I'd say the most likely thing that could happen if SI is "wildly successful" is that PI may become motivated to work on something in the similar realm as SI during the free-time (as they apparently did with SI), or when they have absolutely no better ideas of what they could do for DLC content.
This one is not very plausible... The Aztec Empire was a alliance between three city states. This alliance start 1428. So not in the time where the aztecs conquere Europe in this game. And look at
this map. The dark red part is the land of the aztecs untill 1440. The have no connection to the sea. And they had never big enough ships for this travel. And... I can found many more points. This DLC isn't plausible it couldn't really happen. I personaly don't like this DLC and wouldn't buy it.
But all the "I want a fucking preposterous DLC!" threads are really annoying. I want that paradox make reasonable DLCs and Expansions. Like Sword of Islam of the Lagcy of Rome. We have so many construction zones! Republics, Navy, Trade, Catholic Church, Pagans etc. And all this people want that paradox waste time to this? One funny DLC is okay... I have no problem with this, I musn't buy it... But that are really to many. And all are the same "X shall conquer Europe!" Ony X is allways another thing cthulhu, Aliens, Zombies. This should be fun? Modders can to this to! This is easily done...
Hey.... This is the idea! I make a zombie cthulhu alien (Yes! The alien cthulhu as zombie!) mod. So all this people have fun and paradox don't need time for this. I need someone who can make the spirites!
Sorry if all this sound very aggressiv... But I'm not very happy about the situation... And the Aztec DLC is not the real problem...