Nintendo is in the fortunate position that they needn't rely on third party games. They have a pretty well stocked catalog themselves. Mario, Smash Brothers, now probably Pokemon, too, what more "exclusives" do you need?
Noticeably, Nintendo has always been the "odd man out" when it came to games libraries. Non-exclusives for XB or PS usually eventually came out for the other system, but Nintendo always had a nearly distinct game library from the other two. That does matter. It means that Nintendo doesn't have to compete with them on their turf. XB and PS have always been busy one-up'ing each other in specs, mostly because, well, if you have the same games on both systems, what matters is simply "where does it look better" and "where does it run more smoothly". If you're dealing with a completely different game base, you can't compare. More over, the games have a vastly different focus. Where PS and XB focus on action oriented games where multiplayer is mostly a thing of online gaming, Nintendo's consoles always had a distinct focus on local multiplayer, complete with a lineup of party games and controllers that were, compared to XB and PS controllers, VERY basic and simplified, so you didn't first have to learn to play, you could simply pick them up and play. Maybe not perfectly, but most games were of the "easy to pick up" kind that lends itself well to party gaming.
So I do think that Nintendo can (and will) survive as this "niche" player. It has a few strong IPs in their pocket, and since they themselves own that IP, there is exactly zero danger that this IP would ever go to another console, hoping for a bigger market share there. Even the WiiU, which was a train wreck from conception to inception to realization to actually playing with that piece of garbage, couldn't prevent that. I still don't see why anyone thought the WiiU was a good idea, and I don't know anyone who really wanted that console, but, well, there's nowhere else you could play Mario games. And Smash Brothers. And the other consoles simply suck as party consoles. Even more than the WiiU, believe it or not.