Update
Nintendo has been in touch since we first reported that Mario Kart 8 and Super Smash Bros. 4 were coming in spring 2014. Germany Nintendo's Bernd Fakesch had earlier suggested that both games were due in Spring 2014, but that is seemingly incorrect: Super Smash Bros. is still only dated for 2014 - Mario Kart 8 is still expected in spring.
ORIGINAL STORY
It would appear as if Nintendo's two biggest sure fire best sellers aren't all that far away from release as Nintendo Germany's Bernd Fakesch stated in an interview with Neckar Chronik.
"Für nächstes Frühjahr sind außerdem mit Mario Kart 8 und Super Smash Bros. zwei weitere große Lizenzspiele für unsere TV-Konsole angekündigt."
"For next spring we're also announcing two more big license titles titles Mario Kart 8 and Super Smash Bros." (rough translation)
Speculation is that Nintendo will announce the release dates of both titles in a Nintendo Direct in January.