Nate is still alive
More than that; he will be the designer for the next film. Amanda already said if you didn't see it, it didn't happen. It's given more weight because Ben survived the quicksand trap as well. Nate was already the winner of a game, and experienced a few others in this film. He has qualifications at least equal to Amanda in that regard.- Alternately, Danny could be the next designer, having been revived from unconsciousness after his fall through the ice in the first film. He's the only competitor we know of who'd actually liked escape rooms, after all: he might have better ideas than Nate would.
Everything is fake
There is a reason why none of the other winners properly explained how/why they survived their Escape Rooms despite Minos apparently killing their winners; they aren't actually past winners. Amanda's fate already showed that they are willing and able to psychologically break people to do things they might never have considered doing on their own accord; is it so much of a stretch to assume that Minos could have manipulated four people into either acting like or outright believing that they had taken part in past Escape Rooms that either never existed or didn't feature them directly?Considering that they have such a vested interest in Zoey playing their originally-planned game on that plane, it doesn't seem implausible that Minos would go to such lengths to recruit her, even if it also raises some disturbing implications about why they're so interested in Zoey in particular...
Minos is a team of reality benders
And they have the power to make everything an escape room. How did they know that Sonya would go into the sauna in the beginning? You may argue that the entire building is rigged with escape rooms. However, at the end of the film, how did they know that Zoey and Ben would be taking that specific flight and rig it before it takes off while nobody notices? Heck, in the original film, how did the TV static room work at all? How did they fit everything into a single building in Chicago? And how did they wipe the evidence of it ever existing? I think that the answer is that they're reality benders, and they used their power to make deadly escape rooms.