The biggest threat to Nintendo's position in the market in the future is cloud gaming services, which will allow high-end PC games to run on almost any device. If services like Google Stadia and xCloud work in the wild as they have been advertised, then the Nintendo Switch's status as a portable system will be threatened.
The fact that cloud gaming services work on smartphones means that the potential audience is so much bigger, as it's estimated that they are owned by over five billion people around the world. Not all of those people will have access to cloud gaming at first, but the big markets like the US will, which will act as the testing ground for these services in other regions in the future.
Is nintendo doomed again?