I see him as polygons and sometimes sprites.
Seriously though Mario was never created with the intention of standing out remember he was 'Jumpman' so nintendo just stuck with that simplistic idea from the 80's, and in the 80's character development was not important.
Also I don't think another sunshine game would be beneficial to the wiiU at this point after all it is probably one of the least liked mainline mario games.
My 3ds friendcode: 5413-0232-9676 (G-cyber)