If you look at what happend with Switch it seems that Nintendo have first released remakes/remasters of old relatively inactive franchises before releasing a brand new entry. Examples include Samus Returns before Metroid Dread, Link's Awakening before Echoes of Wisdom and Famicom Detective Club before Emio.
Based on these precedents I'd say the obvious franchise to make a comeback is Donkey Kong, probably a 2D Country game developed by EPD Tokyo since they recruited for a 2D game a few years ago. I'd also cite Advance Wars, Another Code and maybe F-Zero.