not sure how long will take, but it almost seems a given, no game has ever proven it can sell more than 20 million except for nintendo games.
so given enough time it only makes sense that future nintendo releases that have potential to sell 20 million will fill up the top. sure it may take a long time with waiting for future mario's or pokemon or other games. but until a non nintendo game proves it can sell 20+ million then i don't see how you can't believe that nintendo will own the top