There hasn't been a new game in a long while, but I think it's important to keep in mind how often Nintendo franchises sometimes go on hiatus.
Metroid had one in 1995-2001 and another briefer one in 2011-2015. Donkey Kong Country had no brand new installment in 1997-2009, Star Fox was MIA in 2007-2015. Kid Icarus also vanished from 1992 onwards, only to resurface in 2012 and go back on the backburner again right afterwards.
We will see another Wario Land at some point, the bigger question isn't so much if, but rather when.