Looking at the games that are being released and have been released, the big theme among them is how different they are from there predecessors.
Take Pokemon Sun and Moon for example. Though they have their problems, they're some of the most ambitious Pokemon games to date, both tech wise and gameplay wise. They're the only Pokemon games with a really solid story other than Black and White (not counting spinoffs), and are pretty much the only ones with any sort of character development. Gameplay wise, pretty much replacing Megas with Z moves is one of the biggest changes mechanically we've ever seen. It would be like if the Sinnoh games removed double battles after RSE.
Similarly, Zelda: Breath of the Wild seems like it's the most story-driven Zelda game ever, based on the trailers. And a complete open world? That hasn't been seen since Zelda 2. They're even making yhe combat more complicated and difficult, looking like somewhere in the middle between Ocarina of Time and Dark Souls.
And then there's Super Mario Odyssey going back to a sandbox type game like Sunshine and 64. I can guarantee that almost no one was expecting this. Maybe something more akin to Galaxy, but not this.
All this is making me excited for how they'll change up their other games, like Fire Emblem, Animal Crossing, Mario Kart, or even Star Fox.
And maybe Metroid too