what do you guys think?

Very unllikely: many people are whaling for 5* servant (even more than 1000$ for one servant). And Jalter is around the corner...

Why would that happen? Can't even think about a reason for na server closing, and yes, release all storys and events it's the objective. Jp server is active till now since 2015.

Considering that it's the 64th highest grossing app in the apple app store (which is pretty high all things considered), I'd say that it's doing pretty well, and unless the game gets banned, suddenly manages to lose a significant portion of players (which is unlikely), or in Japan the app closes down (I think that the American servers are also managed in Japan) the American version is likely to stay.

I don't have a issue with the NA server to close down.