Obviously the big thing a lot of people are wondering about is the Wayforward game. Is Wayforward working with Nintendo on a revival of an old IP? Or is this a third party IP? Given it's specified it's a franchise Wayforward has NOT worked with in the past this means we can rule out stuff like Contra (they made Contra 4 on the DS), Double Dragon (they made Neon), River City (they just put out River City Girls last year), and A Boy and His Blob (an old NES IP that got a surprise revival on the Wii a decade ago and has been ported to a few other platforms since).
I'm seeing some people speculate that if it's a Nintendo IP then people are hoping for something like Metroid (either Metroid 5 or a remake of Fusion) or a revival of Wario Land.